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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.