Fist time mom, and first time using wearables. I am size 15-16; and as recommended I’m using the 15mm inserts. But it doesn’t feel quite right, but I can’t tell the difference between 15 and 17 either. I used to have 19 inserts on my spectra, so I don’t know if should use 19mm ones? Anyone w the size as me that could give me their input
If you have measured your nipple and it’s 16mm, I believe you should be using the 19mm. I’m 18 and use a 21
Hi mama! 
We’d suggest using the eufy nipple sizing card that comes with your pump — it helps to stimulate your nipple a bit before measuring for a more accurate size. Based on that measurement, try both one size up and one size down from what it suggests, and see which insert feels the most comfortable and gives you the best output. Every mama’s body is a little different, so a bit of trial and error can help you find your perfect fit! 