Oregon 34-820 Flat Idler Pulley Replacement for Murray 300841 Belt tension idler, composite material OD: 4-3/4", flat OD: 4" Flat width: 1", Overall width: 1-5/15", Bore: 3/8, Offset: 1/8" For 38" and 39" tractor decks Replaces Murray # 300841