When it Comes to Pumping Flanges… Size Matters!

If you are a nursing/pumping mama, you already know that pumping can be a pain in the butt but do you know for sure if you are using the correct size flanges?  Having the right flange size is really important.  Using the right size can seriously impact your relationship with your pump… it could mean the difference of a few more ounces of milk and obviously it makes a huge difference in comfort.


Medela Flanges – Photo Courtesy of Amazon.com


I discovered about 8 months into my nursing/pumping journey that I had been using the wrong flange size and I WISH that I had known this much earlier on.   One of the biggest reasons that it took me so long to realize that I was using the wrong size is that as a new mom I had no clue how the flange was supposed to fit or how the pump was supposed to feel.  This topic wasn’t even touched on (as far as I can remember) in my breastfeeding class that I took before my son was born and unfortunately with breast pumps and their subsequent parts, there’s no “try before you buy” option so I didn’t have anything to compare.  Sure, I read the instruction book that came with my pump and there was a diagram in it that showed what a too big and too small flange should look like but do you have any idea how hard it is to judge if your flange fits the way it shows in the picture? (Below is a picture similar to the diagram in my user manual) I mean my pump happened to come with two sizes of flanges and I knew for sure that one size was too big but if the other one was right?  It seemed OK!  To be honest I didn’t even know that there were additional sizes available that didn’t come with the pump and when I did find out… I assumed that they only came bigger (because that what was always discussed when I heard/saw it brought up) rather than the smaller size that I actually needed.


Photo Credit: Medela.com  


The other reason that I waited so long is that the flanges that I had were working and I wasn’t exclusively pumping so I figured it wasn’t worth stressing over.  I had to pump in the beginning when my son was a newborn to protect my supply because he was so sleepy but after that I pumped primarily to have the option of bottle feeding around family members who were not crazy about my choice to breastfeed or to be able to leave milk for another caregiver if I was out without baby.

Every one’s anatomy is totally different.  We all come in different shapes and sizes and it’s unfair to assume that what works for one mom will work for another.  The flanges that I was using were OK… I mean, if I’m being completely honest, I’ll still reach for them in a pinch if my other sets are in the dishwasher.  However, when I pump using the bigger size I get less milk output and my nipples look reddish purple and slightly swollen after pumping. If I was an exclusive pumper… this would be a much bigger problem.  I imagine that my nipples would be sore and that I would likely not have pumped for over a year.  I also doubt that I would have wanted to nurse my son directly after pumping with my nipples in that state if I was pumping multiple times a day.

How did I finally figure out I was using the wrong size?  Believe it or not, I was watching a live stream on Shari Criso’s page.  If you are not familiar with her she is an IBCLC and you can find her Facebook page here.  She was doing a breastfeeding Q&A and she was discussing nipple shields.  (Bear with me, I know this seems like a different topic, but I promise it’s related!)  Shari was explaining that if you are using a shield, it’s important to have it sized correctly.  She commented that most people are not a size 20 (which happens to be what I was using).  This got me thinking…

I knew for sure that I was using the right size shield because in the hospital when my son was born, I really struggled to get him to latch.  The nurses suggested using a shield but it wasn’t until the last day of my hospital stay, when we finally got my son to latch, that a different nurse told me that she thought I had been given a shield two sizes too big by the other nurse.  I am forever thankful to this nurse (who I am now lucky enough to call a friend) because without her, I’m really not sure that I would be nursing today.  Anyway, the point is, I knew for sure that I was using the right size nipple shield.  It had saved my nursing relationship and had never caused me any pain or discomfort.

Nipple Shield Photo Credit: Amazon.com

I commented on Shari’s livestream that I was in fact using a shield that small and that it fit perfectly and she asked what size pumping flange I was using.  I was using a 24mm flange!  What I didn’t know is that if you are using a shield, the flange should be the same size!  A few days later in my breastfeeding support group I brought my flange with me and asked my IBCLC (who is awesome, for the record) if she thought I was using the wrong size.  She said that it was a tough call and suggested that it might be worth trying the smaller size just to see.

*Side note: Most flanges aren’t terribly expensive but before you invest in a new set… check with your insurance company!  I am so glad that I did because it turns out that my insurance company covers extra parts for my pump for up to three years!  Wow!

The only problem was that I was using a Spectra pump which I had recently switched to from my Medela.  (More on this in a future post!)  Unfortunately, my pump supplier did not have the Spectra flanges in the size that I needed.  But lucky for me, the Spectra can be hacked to use Medela parts!  You can also use Maymom parts with the Spectra.  My insurance company actually ended up sending me both Medela Flanges and Maymom flanges.  (Note: smaller sized Spectra flanges are now available on Spectra’s website – at the time they were not!)


Spectra Flange Photo Credit: Amazon.com


Two weeks later (because insurance processing times are SLOW) I had my new smaller flanges in hand and let me tell you what a difference they made!  I was literally able to pump a whole ounce or more with the smaller flanges than I had been able to before and not only that, but my nipples were not swollen and tender afterwards.  Talk about a positive change! I will note though, that all flanges are not created equal.  By that I mean that even if they are same size, they do not all fit the same.  I found that the Medela flanges (which are two parts) versus the Maymom ones (one piece) were a better fit and so again, I found it helpful to hack my Spectra pump to be able to use them.   (Note: the Maymom flanges come with adapters that allow you to use them with the Spectra pump without “hacking it.”  These adapters can also be used with the Medela parts for easier use with the Spectra pump.)

The bottom line?  If you aren’t responding well to your pump, there could be a number of reasons why.  Before you change the pump you are using consider checking with an IBCLC or at the very least checking this link (Medela) or this link (Spectra) to see if you are using the right flange size.  I have included a Maymom image below that could be helpful too!  It’s also worth checking Google to see if you can “hack” your pump or try a different compatible flange to see if you prefer it.  And lastly, don’t be afraid to check with your insurance to see if they will cover the new parts!  The worst that they can say is no and you might benefit in a big way.


Photo Credit: Maymom


Do you have a similar story?  Leave me a comment and tell me about it!


** Update** Below is another useful guide from Aeroflow. You can find more info on their website here: https://aeroflowbreastpumps.com/blog/breastpump-flange-size-chart


  1. Megan Luevano on March 13, 2019 at 4:40 pm

    Thank you so much for your post! I gave birth to my daughter on December 26th. When I was in the hospital I was using a 30 mm phalange. My nipples were so much bigger. Well I kept using a 24 mm size and they were so sore after pumping. I have been reading and found out that I needed to try a smaller one. My breast and gotten so much smaller in the last couple months. I have a Medela and I bought the 21mm flex fit ones. It’s heaven! I feel so much better and don’t dread having to pump.

    • Lore Slaughter on March 13, 2019 at 5:13 pm

      Hi Megan! I am so glad that my post helped you. Congratulations on your little one!

  2. CS on March 25, 2019 at 4:23 pm

    Thank you for posting this! I was getting frustrated by the size guidelines offered by all the pump companies, which were vague and not helpful. (It looked like my nipple was rubbing AND the areola was being drawn in… so both too large and too small?) Because of your post, I was able to find the right size flange. Thank you!!

    • Lore Slaughter on March 27, 2019 at 5:34 pm

      Hi CS! I am SO glad that I was able to help! I agree that sometimes the info included with your pump can be very confusing. Wishing you the very best.

    • TeeJay on July 11, 2019 at 8:38 pm

      Hi, I’m having same issue. I delivered on June 3rd and my baby is a premie, in NICU. I have to extensively pump, but have not been able to establish the correct flange size yet! Pumping has become so painfully! The sizes I tried are too big or too small. Can you please suggest on how did you have it rectified. Thanks!

      • Lore Slaughter on July 12, 2019 at 11:29 am

        Hi TeeJay,

        Finding the right size flange can be difficult to figure out on your own. If you have already tried a few sizes and are still struggling my best suggestion would be to see a lactation consultant who could look at the flange that you are using and evaluate it’s fit. If you want to attempt sizing your nipples yourself again you can try this “nipple ruler” from Maymom: http://www.maymom.com/nippleruler/nippleruler.pdf . Keep in mind that different flange brands might fit differently too so once you figure out your size, you can try a compatible alternative brand (such as maymom) instead of the flange brand that actually goes with your pump. I hope that this helps. Good Luck! Congrats on your new baby.

    • Shannon on August 16, 2019 at 11:24 am

      Thank you for posting this! I saw a diagram of the sizing and thought “well none of these actually fit me if your whole areola isn’t supposed to be in the tunnel part” so I contacted a lactation Consultant and she wanted me to go home and take pictures in a 30mm, 27mm, and 24mm flange… ALL TOO BIG! But us new moms/pump users stumble upon to most of this info accidentally so I’m grateful to you for helping other moms out!

      • Lore Slaughter on August 16, 2019 at 11:44 am

        Hi Shannon. I am so glad that you found my post helpful. I feel like it seems to be more common for moms to need to size up than size down so it can be a little tougher for those of us who need smaller than “standard” sizes! Congratulations on your baby <3

    • Sara on December 10, 2019 at 5:21 am

      I’m still so confused on which size to use. My right side is comfortable with 30mm. My left looks slightly smaller and the side rubs on the side with a 30mm and irritates the Mongomery tubercles. I tried a 27mm on the left and it feels pinchy. Any suggestions??

      • Amanda on December 10, 2019 at 9:14 am

        Hi Sara! Have you considered trying a different brand of pump flanges? The shape of the Pumpin’ Pals might be different enough where it wouldn’t rub on your left breast. It depends though if the pump you have would be compatible with the Pumpin’ Pals, plus the sizing is a little different on them so you would need to see what a 31mm size would convert to on the Pumpin’ Pals. That’s the one suggestion that comes to mind! I hope it might be helpful!! – Amanda

    • Brandi on March 1, 2021 at 1:34 am

      So you were able to find one without the areola being pulled in? That’s my biggest problem and I keep going down in sizes but it doesn’t seem to work. I’m using a 19mm one now.

  3. Dikaha on April 20, 2019 at 2:06 am

    I am going through same issue, i am realising that I need small flanges, currently using 24 mm with spectra s2. But i dnt know how to order these small flange sizes. Can you tell me which one has maymom flanges available. I could not find on aeroflow website. And can I order directly from spectra website?

    • Amanda on April 22, 2019 at 10:33 am

      Hi Dikaha,

      I don’t know if you can order the maymom flanges on Spectra’s website but you may want to see if Spectra has a smaller flange they make that they sell directly. If not you should be able to find maymom flanges on Amazon.com. Hope that helps!

    • Lore Slaughter on April 23, 2019 at 5:24 pm

      Hi Dikaha,

      You can order 20mm flanges directly from Spectra (they did not carry them when my son was born). Spectra does not sell Maymom parts. Maymom is a third party but they sell parts compatible with Spectra. Maymom parts are available on Amazon or through some distributors. I personally ordered mine through Baby Pavilion and was able to get them covered by insurance. It may be worth checking to see if Aeroflow can get you the smaller size flanges from Spectra or to check with another distributor. Good Luck!

  4. Natalie.yost12990 on April 25, 2019 at 9:36 pm

    I apologize in advance for the long comment, but I would really like some help figuring out what is going on with me. I ordered a Spectra 2 through Aeroflow and I followed the guidelines on measuring the nipple base. According to the chart, I think I was a 24mm. I breastfeed most the time because I have the hardest time pumping. I make tons of milk for my baby but its like I know I have milk in there, but I just can’t get it out! It is hard for me because it takes me two days to pump a full spectra bottle and MULTIPLE sessions to do it. I dread letting anybody watch my baby for me because its a nightmare trying to get milk pumped out. I go back to work in September. My baby is almost 6 months and after 6 months of this and I decided I was throwing in the towel and going to break the bank and look into other options like the Willow. I get on there today to order the pump and it wants to know the flange side. Naturally I went to click 24mm until I noticed their size chart was different. They offer 24mm and 27mm. I starting reading their sizing guide and it said to hold either a dime, nickel or a quarter in front of your nipple to compare the diameter of the base of the nipple to each coin. IF you are smaller than a dime, than you are a 21mm (which they do not even offer), larger than a dime but smaller than a nickel is a 24 mm and so on. I was smaller than a dime. I thought whoa! now wait a minute here, have I been using the wrong size flange all along which is why I can never pump any milk out?! I am so frustrated! So I ordered a 21mm off of Spectra’s website today to see if it will work for me. What are your thoughts on this?

  5. Natalie.yost12990 on April 25, 2019 at 9:39 pm

    I should add that my reasoning of looking into the willow was because I was thinking of the convenience of being able to wear them all day on the go and constantly have the stimulation in hopes that maybe I would start producing so much, something would happen for me on getting the milk out where I can start building a supply for when I go back to work.

    • Amanda on April 26, 2019 at 6:43 am

      Hi Natalie! I’m going to answer your comments separately since it sounds like the main concern is how much milk you’re able to get out of each pump session and building a supply (this comment strand) then the other about the pump flange size (your other comment). They do connect but it might be easier to answer them separately. Also let me say that I am not a lactation consultant so I do recommend reaching out to a LC for professional advice on this and these comments do not replace medical advice. I can recommend two great IBCLC’s if you need help finding one. I am however a mom who exclusively pumped with my son, had a low milk supply and always struggled with pumps. Pumps are notorious for not being as effective as a nursing baby at getting all the milk expressed from your breast, their just not as good. Our bodies sometimes don’t respond as well to a pump as they do to a nursing baby and a lot of milk can be left in our breast. I don’t know if you’re an exclusive pumper or if you nurse your baby as well but they BEST recommendation I have, if you nurse, is nurse baby on one side while pumping at the same time on the other side. This could help with building your milk supply because you’re telling your body baby is demanding a lot more, so produce more and you’re using your body’s natural let down from baby nursing to help the pump express the milk on the other side. If you’re an exclusive pumper then adjusting the pump suction and speed will be important but also try hand expression when you’re done with pumping. Hand expression helps push the remaining milk left over out of the breast. Milk supply does have a lot to do with how much water you drink, your diet, and stress level too so keep that in mind. I can’t speak to the Willow pump, I just haven’t heard them used to get any feedback from moms, I will say my experience when I went to a battery operated pump, it didn’t have the ability to have a strong suction long enough to really do anything. I dreaded if I had to rely on my battery in my pump because after a few minutes it lost the suction power I needed. I hope all that info help and in a little bit I’ll answer your pump flange question as well! Thanks so much Natalie!! Cheers, Amanda

      • Lore Slaughter on April 27, 2019 at 9:01 am

        Hi Natalie,

        As Amanda said, my best suggestion would be to seek out the help of a professional LC. They would be able to offer the best personalized help. I am NOT a medical professional or LC. That said, I struggled with pumping too. As Amanda mentioned, my best pumping sessions where when I pumped one side while nursing my son of the other. It takes a little practice but using a Rumina pump and nurse bra makes this 1000 times easier! (IMO) The output from your pump is often no where near what your baby can remove by directly nursing. I did not respond well to my pump alone and if I was able to get 2 or 3 oz per pumping session that was good for me. I can understand that this can be extra stressful as a mom who is going back to work. In addition to trying to pump and nurse, you could also try power pumping to try to increase your supply. I talked a little about it in my post about low milk supply. You can find it here: https://rumina.wpengine.com/the-truth-about-low-milk-supply/

        As far as the flange size, I too was using flanges that were really too big for me for months until I realized it and for what it’s worth, my IBCLC told me that nipple size can change! There’s definitely no harm in trying to smaller flange size. Give the new size a few days (it might take your body a few days to adjust) and see how they feel and if it makes a difference in your output. I would also recommend playing with the settings on your Spectra. The Spectra is an awesome pump but it definitely has a bit more of a learning curve compared to other pumps due to the fact that you can personalize the settings so much. You may find that you just need to adjust some of the settings a bit! This is something that an LC could help you with.

        As far as the Willow pump, I don’t have any personal experience but I have a friend who used it and LOVED it. There are some great resource groups for it on Facebook if you have additional questions about it but I would definitely give your Spectra another chance before you invest in another pump (especially if you really do need the smaller flange size!) Good luck! I hope this info helps. Lore~

  6. Natalie.yost12990 on April 28, 2019 at 9:53 pm

    Thanks so much!!! I appreciate your responses!! That is what I will do!

  7. Anuj Sharma on August 16, 2019 at 9:53 pm

    I love to read your information.

    • Lore Slaughter on August 19, 2019 at 7:52 am

      Hi Anuj,
      I am so glad that you find it helpful! Thanks for reading. 🙂

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