3" random technologys downpipes. These a 4 bolt, so they will bolt up to stock turbos, sport 500, sport 600, or any other T2 flanged turbo. They will not bolt up to most test pipes, cause they have a 3" outlet. An adapter can easiely be made by any exhaust shop though. Dyno proven to gain 36 ft./lbs. of torque, and 25 HP. Check out random technologs web site. They may not be as popular as the split DP design, but this is a great deal for a build up on a budget. $70 shipped. Prefer paypal. Thanks... DJ Skone email--->djskone@hotmail.com