Turning Point 31522140 Express Large Diameter Stainless Steel Propeller with 4-3/4" Gearcase - 4 Blade / 14-1/2 x 21 / Left Hand Stainless steel prop made from 15-5 stainless steel, which gets harder and stronger with age Higher rake angles tighten the vortex produced by the propellers, adding to boat lift and overall performance Improves handling and boat lift through aggressive rake and cupping Tuned progressive pitch angles accelerate and channel water to minimize slip and increase performance and fuel economy Tuned vents for fast hole shot