Malibu: 3431934 Prop Shaft, 1-1/4 x 54 w/BW5 Rev Coupler ..Shaft diameter: 1-1/4″. Shaft length: 54″ (from flange to end of prop shaft) Coupler diameter: 5″. The coupler is a reverse mount (shaft goes through the v-drive and connects to the front of the v-drive. Factory Shaft & Coupler used on Malibu Boats equipped with a velvet drive v-drive or thru mount ZF v-drive.