My nipple size is 13mm, I will need a smaller size flange than 19mm, am I still be able to use Hegen PCTO™ Manual Breast Pump Kit (SoftSqround™)?

Yes! If you have a nipple measurement of 13mm (13mm + 4mm = 17mm), you will need to purchase a 17mm Flange insert and place it onto our 25mm Flange and you are good to go!