Martin idlers are smooth-running and available in oil-impregnated, sintered bronze, extra-duty bearing press-fitted in sprocket and a hardened steel journal case for maximum resistance to wear. Steel sprockets used in Martin idlers are accurately machined (not stamped) the same as sprockets normally supplied for power transmission use. Martin can also alter existing sprockets and install bearings to make custom idlers. Martin Ball Bearing Idler Sprocket, 3/4 in Bore, 4.332 in OD, #80 Chain, 12 Teeth, 1 in Pitch, 3.8637 in Pitch Diameter, 2.66 in Diameter Hub, 0.96 in Length Through Bore, Plastic