Big Gun Exhaust 40-R02 Rev BoxBig Gun Exhaust 40 R02 Rev Box If you are looking to swap out your stock Arctic Cat 500 CDI box, the Big Gun Over Rev Box is an affordable alternative to highly priced OEM replacement boxes. It increases the overall RPM limit over the stock box and advances the timing curve. Increases overall RPM limit from 9,000 to 9,750 Advanced timing curve Easy direct plug in replacement to stock CDI box 6 Month Limited Warranty Big Gun Exhaust 40 R02 Fitment: