This new one-piece universal cap and strap is designed to fit most gravity water fills, threaded or bayonet style with an inside diameter of 1-1/4". The cap is constructed of polar white flexible rubber that resists fading and breakage. Easy to install by slipping the strap over the neck of your water fill then just placing the plug into the opening of the water fill and you are ready to go. No more hard brittle plastic straps or caps to lose or crack.