The Hydro Flip Lid Is The Instant Conversion Kit For Wide Mouth Hydro Flasks. Coffee, Tea And Other Hot Beverages Are Just A Flip Away And Consuming Hot Beverages On The Go Is As Easy As Can Be. Like All Hydro Flask Caps, The Hydro Flip Is Made Out Of And Is Bpa-Free. The Lid Features A Flip-Top Opening With Rubber Stopper To Plug The Opening And Help Prevent Spills When Not In Use. Please Note That The Hydro Flip Lid Does Not Fit On The Older Style Wide Mouth Flasks. To Find Out Which Style Flask You Have And Whether The Hydro Flip Will Fit Yours, Check Out The Hydro Flip Fit Guide. Please Note That The Hydro Flip Lid Is Not Leak Proof.