Constructed of stainless steel and 6061-T6 billet aluminum, unlike the stock pumps, which are made from weaker cast aluminum, plastic and brassThese performance pumps are a direct replacement for the inefficient OEM aluminum 6-vane stator sectionIncludes 12-vane stainless pump, pump cone and dual cowling with brass fittings144 mm stator requires the use of a large hub Magnum impeller part# 4809-0196 (12/18 pitch) or part 4809-0197 (13/19 pitch) sold separately.Use OEM Yamaha bearings and seals.Spacer not required.