Our silicone flanges should stay securely seated in the collar ring that attaches to the adapter that screws onto the bottle. Here are things to check if they don't:

Are you putting a little water (or saliva) around the base of the tunnel before putting it into the collar ring as shown in our silicone instructions? It can also help to use a twisting motion to help it get in deeper.  The flange should go at least 80% of the way in the collar ring but shouldn't go past the end of the collar ring.

Are you using a soap that leaves a lubricating film on silicone?  We find that many kinds of dish and dishwasher soaps use an ingredient to prevent water spots that bonds to silicone making them slippery.  We recommend Dawn Ultra (with yellow ducks on the label) because it doesn't have this ingredient. 

Another option is
 our Silicone Cleaner that can be used after or in place of soap. It removes soap buildup and restores silicone flanges to like-new condition.

Reviewed by Diana West, IBCLC

June 10, 2021