Product Description ARC’s header and muffler kit for the AKRA/WKA clone Box Stock class. Looking at the picture above, it is easy to see what sets ARC’s header apart. The flange is funneled into the header pipe so exhaust gases flow smoothly out of the exhaust port. Contains a ARC_DJ-1138B CNC port-matched header, RLV_4117 “Mini 91” muffler, and Pre-bent steel brace. Second angle of the pipe is shown for the funneled flange view. Only one pipe is included. Predator 212 engines will need a small modification to the mounting holes to fit the engine.