Piston Std / Briggs & Stratton 499956Pack Size:1Briggs & Stratton 391285, Briggs & Stratton 394661, Briggs & Stratton 394955, Briggs & Stratton 499282, Briggs & Stratton 498584, Briggs & Stratton 499956, Briggs & Stratton 499284ESF 163-150, Foley/Belsaw 5978374, Foley/PLP 163-150, Laser L5639, Laser 94228, Oregon 36-312, Prime Line 7-03843, Prime Line 7-03513, Rotary 6725, Sunbelt SB-6725, Sunbelt B1SB6725Briggs & Stratton 220000-222000, 252000-257000, 280000-286000,389700 and 400000-422000Ethanol: Not compatible with greater than 10% ethanol fuel, Cylinder Bore Size: 3.4365"-3.4375"