2.5" T3/t4 5-bolt stainless steel TIG welded downpipe. 90 Degree Downpipe: 2.5" OD. 1x T3/T4 90 Degree Downpipe. 5 Bolt Flange: 2.25" ID. 1x 5 Bolt Flange. This provides a simple starter solution for connecting your turbo's exhaust to your existing exhaust system.