The "Orange" or "Red" Spring. Use as exhaust spring when using stock exhaust valve and ARC DJ-1046 Spring retainer Use as medium spring for intake and exhaust when using our stainless (DJ-1121,22 and 26) valves. Use as medium spring for intake and exhaust on BSP/clone/GX200when using stock valves and stock retainers. (for BP Class) In the Superbox class, use this spring on the exhaust with stock valve and aftermarket retainer for good results. For more info, download our spring rate chart here.