Piston +.020 / Briggs & Stratton 391288Pack Size:1Briggs & Stratton 391288, Briggs & Stratton 394663, Briggs & Stratton 394957, Briggs & Stratton 499290, Briggs & Stratton 498586, Briggs & Stratton 499958, Briggs & Stratton 499292ESF 163-152, Foley/Belsaw 5979653, Foley/PLP 163-152, Laser 97351, Oregon 36-314, Oregon 36-217, Prime Line 7-03517, Prime Line 7-03510, Prime Line 7-03837, Rotary 8826, Sunbelt SB-8826, Sunbelt B1SB8826Briggs & Stratton 220000-222000, 252000-257000, 280000-286000 and 400000-422000Ethanol: Not compatible with greater than 10% ethanol fuel, Cylinder Bore Size: 3.4565"-3.4575"