Pump Drive Idler pulley replaces Exmark/Toro OEM#'s: 1-633166, 633166. Stens# 280870, 280-870. Rotary# 13-9793, 9793. Fits some 52", 60" and 72" Exmark Lazer Z model mowers and Toro Z 500's Z Master 2004 & newer 60", 72" decks; Z 250's Z Master 742XX series 1999-2007 52", 60" and 72" decks. Refer to your manual to match by OEM#.