New, shorter, Dyno Tuned high flow design by ARC for the AKRA and WKA Box Stock Class. The flanges are 1/4" thick and are CNC port matched to the exhaust ports of the BSP / Clone and GX200 engines. The Pipe is high quality 16 GA High carbon steel for strength and durability. The collar is threaded for easy installation and removal of the RLV "mini 91" RLV-4117 muffler. This is the header that comes standard with our DJ-1138RLV header/muffler kit.