New "B" Type Sprockets for #415 Chain."B" Type Engine Sprockets have a hub on one side. Made of case-hardened steel, with hobbed teeth, these "B" Type Sprockets for #415 Chain have a 3/16" Keyway, Two 5/16-18 Set Screws and a 3/4" Bore. Your choice of 10 through 14 teeth.