The center riser is a two-piece aluminum manifold/riser ideally suited for replacement use where riser protection is required. The Barr Center Riser aluminum manifold/riser uses flexible exhaust hose which facilitates connection to existing exhaust lines. All elbows (cast iron) can swivel inboard or outboard for perfect fit. The Barr Center Riser aluminum manifold/riser is designed to limit back presure on the engine, resulting in more efficient engine performance. The manifold and riser can be reversed and will fit either side of the engine. The Barr Center Riser aluminum manifold/riser is cast of 356 T6 aluminum, well suited for fresh water marine applications. Barr Marine