Tube diameter -2,5" (63mm) Inlet diameter - 63mm Pipe diameter at joint with centre section 51mm Mounting flange: OEM Used to replace a factory fitted DPF and after its installation exhaust system is unblocked and that noticeably improves the "bottom" of the engine. The so-called turbo hole effect disappears and power and torque increases. Compare to similar products, our downpipes are made of high-grade stainless steel SS304 with a thicker wall (1.5 mm - competitive products have a wall of 1.2 mm which can crack or warp) Downpipe for : BMW E39 M57,525D 530D, 1997-2003 ,2163,184,193hp