This is the stainless steel weld flange kit for an HX40 style turbo outlet. The OD measures 4” and will allow you to weld a 3.5” downpipe to the ID of the flange, or a 4” downpipe to the OD of the flange. This is typically used for 2nd gen Cummins upgrades that use an HX40 outlet turbo. Kit includes flange and clamp *This outlet flange is designed as a standard exhaust component that does not remove, eliminate, delete, or alter the effectiveness of any emissions control system, including diesel particulate filter (DPF) systems, selective reduction catalyst (SCR) systems, or exhaust gas recirculation (EGR) systems. This product is not intended for off-road, racing, or competition use and is for road vehicles. Per the Clean Air Act.