Find your flange size
By The Zomee Team · Updated July 12, 2026
To find your flange size, measure the diameter of your nipple in millimeters, then match that number to your pump's sizes in the charts below. Measure the nipple only, not the wider areola, and measure both sides.
Zomee flanges run from 15 mm to 32 mm, with soft sizing inserts from 13 mm to 21 mm, one of the widest ranges available. The Mother's Nature™ W1 and H1 and the Zomee Fit include a nipple measuring ruler in the box, and the printable ruler on this page works for every pump. If none of the included sizes fit, The Perfect Fit Promise sends you a pair in the size you need at no extra cost, and The Mom Line™ will help you measure if you want a second opinion.
Why flange fit matters
Every flange has a tunnel, the part your nipple is pulled into as the pump draws milk. The tunnel's diameter is different for each flange size, and getting that diameter right is essential for effective, comfortable pumping.
A wrong size usually shows up as weak suction or discomfort. Incorrect flange size is one of the most common causes of low or no suction that The Mom Line hears about, and the most common reason a brand-new pump seems to have none at all. Many moms pump with whatever sizes came in the box and never check the fit.
Fit is not permanent, either. Flange size can change between pregnancies, and we always re-measure: a mom on her second or third baby may assume her earlier size still fits. Measure again with each baby.
Step by step
How to measure your flange size
- 1Get a nipple rulerUse the Zomee nipple measuring ruler that ships in the box with the Mother's Nature W1 and H1 and the Zomee Fit, or print the free ruler on this page at actual size.
- 2Measure your nipple diameterMeasure the width of your nipple in millimeters using the ruler's circles or its millimeter scale. Measure the nipple only, not the wider areola around it.
- 3Measure both sidesMeasure your left and right nipples separately and note both numbers.
- 4Match your measurement to a flange sizeCompare each measurement to your pump's size chart below. Zomee flanges run from 15 mm to 32 mm, with inserts from 13 mm to 21 mm, and if you land between two sizes, The Mom Line can help you choose.
- 5Request the size you needIf the size you need did not come in your pump's box, request it through The Perfect Fit Promise and Zomee will send you a pair in your size at no extra cost.
How a wrong size shows up
Start with how a session goes. If your pump is brand new and seems to have no suction, check the flange size before assuming a defect: an incorrect size is the most common reason a new pump seems to have none. And if the diaphragms are moving but little milk is coming, size is the first thing to rule out.
Timing tells you a lot. A pump that worked well and then suddenly lost suction usually is not a flange problem; the usual cause is worn or warped parts, especially duckbill valves, which wear with regular use and with over-sterilizing and need replacing every 1 to 3 months.
When something feels off and you are not sure why, re-measure and call The Mom Line. A short call with a lactation consultant settles a sizing question faster than guessing.
The ruler
Print a nipple measuring ruler
You can measure today, even if your pump has not arrived. Print the nipple ruler below on any printer, check the scale, and you will have your measurement in a few minutes.
The printed ruler includes sizing circles, a millimeter scale, and a scale-check bar, because printers and browsers like to shrink pages to fit. A shrunken ruler skews every measurement, so confirm the scale before you trust it.
- Print the ruler at 100 percent, sometimes labeled actual size, with fit-to-page scaling turned off.
- Hold a standard bank card against the check bar; the two should match exactly in width. If they do not, reprint at 100 percent before measuring.
- Measure your nipple only, not the areola, using the circles or the millimeter scale, and measure both sides.
- Match each measurement to your pump's sizes in the charts on this page, and ask The Mom Line if you land between sizes.
By pump
Sizes in the box, sizes you can add
Every Zomee pump ships with more than one flange size, and more sizes are available for each. Find your pump below to see what is in the box and how to request them.
Across the line, Zomee flanges run from 15 mm to 32 mm, with inserts from 13 mm to 21 mm. If you are still deciding which pump is yours, answer three questions in the pump quiz and we will find your match; the sizing method here works the same on all four.
| Pump | In the box | More sizes |
|---|---|---|
| Mother's Nature W1 | 24 mm warming breast shields plus 15, 17, 19, and 21 mm inserts, two of each, and a nipple measuring ruler | Flanges from 15 mm to 32 mm and inserts from 13 mm to 21 mm come free through The Perfect Fit Promise. |
| Mother's Nature H1 | 19 mm and 24 mm Mother's Nature flanges, two of each, plus a nipple ruler | Flanges from 15 mm to 32 mm come free through The Perfect Fit Promise, and the H1 also works with Z2 Breast Shield Kits in 15, 19, 21, and 24 mm. |
| Zomee Z2 | 17, 19, 21, and 24 mm flanges, two of each; the collection cups bundle adds cups that take 24 mm shields with 19 and 21 mm inserts | Flanges from 15 mm to 32 mm and inserts from 13 mm to 21 mm come free through The Perfect Fit Promise; the Z2 Breast Shield Kit comes in 15, 19, 21, and 24 mm. |
| Zomee Z2 Shabbat Mode™ Edition | 17, 19, 21, and 24 mm flanges, two of each, plus hands-free collection cups that take 24 mm shields with 19 and 21 mm inserts | Same as the Z2. |
| Zomee Fit | 25 mm breast shields with 17 mm and 21 mm inserts, two of each, plus a nipple ruler and sizing guide | Flanges from 15 mm to 32 mm and inserts from 13 mm to 21 mm come free through The Perfect Fit Promise; the shop carries Fit Silicone Inserts in 13, 15, 17, 19, and 21 mm and the Fit Breast Shield Kit in 17, 19, 21, and 24 mm. |
The Perfect Fit Promise
Sizing comes with a guarantee. If the breast shields included with your Zomee pump are not your size, we send you a pair in the size you need at no extra cost. The promise comes with every Zomee pump.
There are two ways to use it. Fill out the request form at support.zomee.com/flanges-registration, or contact The Mom Line and a product expert or lactation consultant, a mom herself, will help you measure, confirm your size, and submit the request for you.
Good to know
Sizing questions, answered
What if I measure between two flange sizes?
Contact The Mom Line. Our support team of product experts and lactation consultants, all moms themselves, will help you measure and settle on a size. And if the in-box size you start with turns out wrong, The Perfect Fit Promise covers a pair in the size you actually need at no extra cost.
Does flange size change between pregnancies?
It can. We always re-measure, because a mom on her second or third baby may assume her earlier size still fits. Measure again with each baby before you start pumping.
Can my left and right sides need different flange sizes?
Left and right often respond differently, which is why the H1 gives each side its own motor and controls. Measure each nipple separately. Every Zomee pump includes two flanges of each in-box size, so you can pump with a different size on each side if your measurements call for it.
What flange sizes does Zomee make?
Zomee flanges run from 15 mm to 32 mm, and soft silicone inserts cover 13 mm to 21 mm. The sizes refer to the flange tunnel, the part your nipple is pulled into while you pump; its diameter differs for each size.
Is the printable ruler accurate?
Yes, as long as it prints at actual size. Printers and browsers often scale pages to fit, so the ruler includes a check bar that should exactly match the width of a standard bank card. If the bar and your card line up, the measurements are true; if not, reprint at 100 percent.
Why does my brand-new pump seem to have no suction?
The most common reason is an incorrect flange size, usually from pumping with the sizes that came in the box without measuring first. Measure and try the size that matches before assuming the pump is defective. If a pump that worked well suddenly loses suction, the likely cause is worn parts instead, especially duckbill valves, which need replacing every 1 to 3 months.