Compatibility:Compatible with eufy Breast Pump E10 / E20 / S1 / S1 Pro. Easy to Install and Use: Enjoy hassle-free, simple setup and operation. Sizing Guide: Refer to our sizing guide to select the right size for optimal comfort. Nipple size may change during different breastfeeding stages, requiring different sizes of inserts. We recommend replacing flange inserts every 1 to 2 months. Customized Comfort: Find the perfect fit for your unique needs and experience comfortable, smooth breast pumping with our silicone flange inserts. Safe Material: These flange inserts are made from food-grade soft silicone. Guaranteed Reliability: eufy breast pump accessories are covered by a 90-day limited manufacturer's warranty. Lifespan: Typically lasts 3 months. Replace if suction and performance decrease with use and sterilization, or based on your usage.