This is an excellent 100% rubber open mouth gag. The mouth piece is made of heavy rubber keeping the mouth from closing. The hole is a whopping 1.5 inches in diameter and protrudes 1 inch into the mouth. Measurements: Neck strap adjusts from 17 to 20.5 inches around, Gag tube has 1.5 inch inner diameter, and 1.85 inch outer diameter, Material: Rubber with Metal grommets and buckle, Color: Black