Big Gun Exhaust 40-R29 Rev BoxBig Gun Exhaust 40 R29 Rev Box If you are looking to swap out the stock Yamaha TTR 125 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 Advanced timing curve Easy direct plug in replacement to stock CDI box 6 Month Limited Warranty Big Gun Exhaust 40 R29 Fitment: Yamaha TTR 125 LEX EX LX