You may be glad to know that our flanges comes in the size 24-27mm (instead of a fixed size) because of the unique way in which the flange is designed. Unlike other flanges, the Hegen flanges are curved (and not straight) at the nipple tunnel, which allows mummies between the sizes 21mm to 24mm to use our flanges comfortably.
As a general rule, mummy's nipples may become more erect/swollen after pumping, hence we would highly recommend mummies to provide an allowance of at least 3mm in the selection of flanges. This is so that the nipple does not rub against the nipple tunnel post-pump, etc. If you have a nipple measurement of 21mm, the 24mm flange would be suitable (21+3) or if you have a measurement of 24mm, our flanges are still suitable (24+3).
In the meantime, for mummies requiring a smaller fit, you may actually reduce the nipple tunnel to 15mm, 17mm, 19mm and 21mm by getting these flange inserts.
These inserts can be placed in the flange and you will not need to repurchase or get another flange to fit the above size requirements. This will also allow you to enjoy all the lovely benefits of the Hegen pump without compromising on comfort and efficiency!