Safe and Easy to Clean: KISSBOBO flange inserts are made of food-grade silicone and are BPA-free. They're easy to clean and maintain, so you can use them with confidence. Compatible with most Wearable Breast Pumps: These inserts work with any S9 Pro/S12 Pro Wearable Breast Pump, including popular brands like Momcozy, willow, Luxlady, and more. They're also applicable to most other brands of models for 24-25mm (Freemie) and compatible with MISSAA hands-free breast pump. Perfect fit for your nipples: KISSBOBO Flanges Inserts to help you find the right size for your nipples. They're compatible with Medela 24mm , Willow 24mm flanges, and Momcozy S9 Pro/S12 Pro Wearable Breast pump 24mm cups. They'll reduce the 24-mm shield nipple tunnel down to your correct size (not for 27mm shield). Comfortable and Efficient Pumping: The size of your flange insert is important for comfort and efficient pumping. Some moms experience nipple swelling while milking, so it's important to observe the appearance of the nipple during pumping. We recommend replacing the flange insert every 1 to 2 months to ensure optimal performance.