Review on 🍾 Tastebar Conical Silicone Stoppers, Set of 6: 3 Airlock Stoppers with Hole + 3 Non-Hole Stoppers. Carboy Airlock Stoppers, Silicone Rubber Plugs for Homebrewing Beer/Wine (Size 3) by James Small

They are exactly as described and fit very well in 5 gallon glass bottles. It's good to have 3 with holes and 3 without holes as this allows you to store wine that has a camping lager added to stop fermentation without worrying about a ferment lock for those vessels. Be sure to wash and dry them very thoroughly before putting them in the bottle. Any dust or water on the outside or in the neck of the bottle will cause them to pop out of the bottle. This is normal for a silicone stopper. If properly cleaned and dried you will get a very good seal. I (accidentally) blocked the fermenter and they hold a little pressure inside the jar.