A 57mm outside diameter alloy bend, the useful in-between size when 50mm starts to restrict but a 63mm run simply will not package. It is a common choice for intercooler pipework and intake tracts on mid-capacity turbo engines and on cars where the route between the cooler and throttle body is tight. Cut to length, deburr, and join using silicone couplers with appropriate clamps. Be careful to buy couplers actually made for 57mm rather than assuming a 2 1/4 inch joiner will do, as a slightly oversized coupler on a boosted joint is a reliable way to lose a charge pipe under load.