Not sure the manufacturer of these but were bolted to Hardin Marine BBC manifolds (manifolds not included). No damage or welds. Outlet hose inside diameter is 3.5", mounting flange is 5" diameter with a 4-hole pattern in a 4.25" diameter. They were in a Daytona v-drive but are common in day cruisers, jet boats sanger Raysoncrafts Howards Stevens Casale nicson Edelbrock Hallcraft rex dana eddie