This Fetish Fantasy Extreme Silicone O-Ring Gag is exactly what you need to keep your sub quiet while keeping their mouth wide open for whatever you wish to put in it! The metal O-ring is encased with medical grade silicone that is taste free and gentle on the teeth and gums while remaining sturdy and durable. The belt like straps, also made of Elite Silicone, easily adjusts to fit most sizes.  Inner Diameter: 1.50 Inches.