They are very hard to get to stick, if/when you do they will do what they are intended for then and work fine. It’s just getting them to actually attach that is an issue, took quite a few tries to get them on. They worked as stated once I did though!
NippleSuckers FDA-Approved Silicone Nipple Suction Discreet Package 2-Pack Purple (Suction Cup Dia. 3.18 inch) https://www.amazon.com/dp/B0714MCCL8/ref=cm_sw_r_cp_api_EuBFAbMAVH6Y2