These are the largest and strongest propellers made by Yamaha. They are designed to harness the awesome power of the V8 5.3L outboards and turn it into massive amoutns of thrust. With 21% more blade area than even the largest Saltwater Series II propellers the XL provides the F350 up to 45% more thrust than the 250hp outboards while also providing large offshore boats with plenty of power to plane, accelerate and reach top-end speed. ***NOTE: Saltwater Series XL propellers will ONLY fit Yamaha V8 outboards. No other Yamaha propeller will fit these engines, nor will these propellers fit any other Yamaha outboard model.