S2000 1-piece 4" Aluminum Shaft. This driveshaft is a 4" aluminum unit that uses u-joints on either end, instead of the factory cv design that is notorious for failure at higher horsepower. DSS includes aluminum conversion plates on either end to convert the 4-bolt flange to fit in the 6-bolt factory location. Please specify in comments box if your vehicle is an AP1 or AP2 when ordering.