S&amp,S Cycle S&S 1" Aluminum Carb Spacer/Insulator Block 16-0357 Designed for those carb installations where additional clearance is required between the tank and air cleaner Each spacer block kit comes with an O-ring 1 7/8in. opening: Mounting hole pattern is identical to stock pattern on Tillotson, Bendix and Keihin butterfly type carbs. Use with all S&S 1 7/8in. manifolds, includes O-rings 2 1/16in. opening: Use with all 2 1/16in. manifolds, includes O-ring