[Safe Materials: Our products are made from transparent food-grade silicone material BPA free and are easy to assemble and clean. These accessories are only compatible with 24mm breast shields/flanges and cannot be used with other sizes. Using coconut oil or nipple cream can reduce friction and help prevent nipple damage or irritation. Usage Instructions: Find the correct size that fits your nipple for comfortable breast pumping. It can reduce the nipple channel of the 24mm breast shield/flange to 19mm. Compatibility: The Flange Adaptor is an accessory for wearable breast pumps and can be used with most 24mm breast shield/flange (e.g. NICEGREEN S21/S32 wearable breast pumps) to reduce the nipple channel from 24mm to your desired size (not suitable for 27mm breast shields). Premium Service: Package Include: 2* NICEGREEN LIFE 19mm Flange Insert.]