This is the Carburetor Gasket for the OS Max 2A, 3A, 3H, 20C, 20D, 20H, 2BK, 2BK, 10E(R), 10D and the 40D carbs. This is the gasket that goes between the engine crankcase and the carburetor body. Fits onto the throat of the carb body. FEATURES: Silicone construction INCLUDES: One Carb Gasket REQUIRES: None, item is a stock part SPECS: Inside diameter: 10mm (.39") Gasket thickness: .9mm (.04") COMMENTS: This part can be sometimes be refered to as the carb gasket "o-ring." NNA 12/23/01