How to Tell if Your Breast Pump Flanges Fit

Woman using a breast pump
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The breast pump flange is the part that connects your breast to the pump. Milk will travel down this tube to the bottle or another collection device. All breast pumps come with a set of breast pump flanges. The breast pump flange is typically a 24-27 mm size breast pump flange, which is average size. But not all women fit into these sizes. You can get smaller breast pump flanges or larger flanges.

The sizes range from 21-36 mm in the plastic varieties and there is a 40 mm glass flange available.

To tell if you have the correct breast pump flanges:

  1. Your nipple should move freely in the tunnel of the breast pump.
  2. Your areola should have little or no tissue inside the tunnel of the breast pump.
  3. You should not be able to feel areas of the breast that still have milk inside. (Uneven removal of milk.)
  4. You should not experience pain in your nipple.
  5. You should not see a white circle at the base of the nipple, nor should your nipple blanche.

If you don't have the right size, you will want to see if your breast pump came with other flanges or if you will need to order flanges. If you go up in size, you may be restricted from using some of the softer plastic flanges, like those found on the Avent Breast Pumps (compare prices) and others.

Not having the right size breast pump flange can result in problems.

One problem is that you will not be getting the most amount of breast milk possible. The other potential problem is actually causing nipple damage like rub marks and cuts on the nipple.

Most breast pumps will only come with the 27mm size flange. The other sizes may be available for an extra fee, and that is only for the more common sizes, say 24 mm to 29 mm.

Women with other size needs may have to purchase from other sources that do not make their pump. This can lead to concerns about whether or not the new flanges will work adequately with the pump. The good news is that most will work without a problem.

If you are having trouble trying to figure out what size you need, even with the guidelines, it is perfectly fine to ask for help. You should try to find a lactation consultant to help you. If you do not already have a relationship established with a lactation consultant, call the hospital where you gave birth. Typically they will have someone who is an IBCLC that can help you determine the issue with sizing. You may also try a local breastfeeding store, usually a boutique type place. Sometimes you may even have to do a mail order for alternative sizes, particularly those in the glass model.

Many of the women I have worked with notice a difference almost immediately. The first thing that they notice is that using the breast pump is more comfortable. After that, the amount of breast milk that they are able to pump begins to increase. This is good news for most moms.


Brown, SL. Breast Pump Adverse Events: Reports to the Food and Drug Administration. J Hum Lact May 2005 vol. 21 no. 2 169-174.

Mohrbacher, N, Stock, J. The Breastfeeding Answer Book. 2003.