Stiletto Performance Propellers • Extended Cup • High Rake • Progressive Pitch • High Strength Alloy • Precision Balanced. Performance and value, redefined from Stiletto. The unique high-rake, progressive pitch configuration is designed to help most boats achieve their best overall performance at all throttle levels... low end, mid-range and top end. Manufactured using a durable 15-5 ph one piece stainless steel casting, then polished to a gleaming mirror-like finish. Your propeller is one of the essential links between your boat and the water. Please carefully choose the Stiletto propeller that will best suit your application. Yamaha Outboard:Yamaha sterndrives and V-6 outboards. For the Stiletto propellers above with the first digits of "ST303 and ST304" - use Yamaha #6E5-45987-00-00 thrust washer or equivalent. Important: These recommendations are for single engine installations only. For most twin engine installations, it is necessary to increase the pitch by 4".