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When it comes to wearables, sizing is different — you'll need a fit that's more snug. Most moms find that adding 1-3mm to their nipple size (or 0-2mm if you're pumping with Willow 360) results in optimal output and comfort.
Still need your nipple measurements? Try our sizing guide
|
Measured Nipple Size |
Willow Recommended Size Flange / Insert |
| 9-11mm | 13mm insert in 24mm flange |
| 12-13mm | 15mm insert in 24mm flange |
| 14-15mm | 17mm insert in 24mm flange |
| 16-17mm | 19mm insert in 24mm flange |
| 18-20mm | 21mm flange |
| 21-23mm | 24mm flange |
| 24-26mm | 27mm flange |
Sizing inserts can only be used with a 24mm flange or 24mm container insert.
Questions? Our experts can help.
1-888-WILLOW-3

Step 1: Get a measuring tape
Measure the diameter of your nipple at its base while erect to determine its size accurately.

Step 2: consider sizing up
Most moms find that adding 1-3mm to their nipple size results in optimal output and comfort.

Step 3: take a look at our chart
Match your measurements to our sizing chart to find your recommended size flange / insert.
2 Willow 360 Milk Containers
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For optimal output, replace every 90 days (or when you notice discomfort or signs of wear).
Mom-approved bundles for breast care, milk storage, and pumping on the go
Save on pumping peace of mind with the Willow Go and protective Pump Anywhere Case.
Everything you need to clean and care for your pumps on-the-go.
Yes, you can. Simply pay for your breast pump and accessories using your FSA/HSA debit card at checkout, or pay with another credit card and submit your receipt to your plan administrator for reimbursement.
The right size is key for maximizing comfort and output. Willow offers flanges and containers in size 21mm, 24mm, and 27mm. If you measure smaller than 21mm, we offer Sizing Inserts in sizes 15mm, 17mm, 19mm that snap into our 24mm Flanges and Containers. We strongly recommend measuring yourself to determine your Willow size as it might be different from other pumps you’ve used. Unsure of your size? Visit our sizing guide or check out our exhaustive guide on how to measure your flange size which includes pro tips from Willow’s lactation consultants.
After every use, you can wash by hand or pop the parts in the dishwasher, top rack only.
It’s important to wash breast pumping parts after every session to avoid the growth of bacteria. We also suggest you do not store your Container in the fridge or the freezer. This can lead to decreased performance for the Container.
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