Oregon 78-052 Flat Idler Pulley Lawn Mower Idlers Oregon 78-052 Replacement Flat Idler Pulley 4-1/2" OD, 3-5/8" flat OD , 3/8" ID, 5/8" Flat width, 1" overall width, 1/4" offset Replaces AYP 175820, 539107620