This is the most advanced, easy to install, state of the art standard box on the market today. The torsional drive shaft helps cushion the shock to the outdrive when shifting in and out of gear, and on and off throttle operations. Inferior designed competitor's boxes use a drive shaft that is solid mounted to the flywheel, doing away with your coupler. Their units literally hammer the internal components in your drive, which rapidly accelerates failure.IMCO's torsional driveshaft and the stock MerCruiser rubber coupler are designed to absorb shock resulting from extreme high performance applications and rough water conditions.356 T-6 cast aluminum transom motor mount brackets available. Lightweight super strong cast 356 T-6 aluminum extension boxes, available in 12" neutral set-back.356 T-6 aluminum side mount steering brackets allows ample mounting clearance for optimum K-Plane placement - clears most exhaust ports, swim brackets, etc. - keeps rams on pivot center line.