This is an upgrade from the stock 12mm carb. This carb has a 3mm larger port and has adjustable air/fuel ratio screw. This carb fits the ScooterX Dirt Dog, X-Racer, Powerkart, Baja Go Kart, SkaterX Gas Skateboard, and many other applications. Most commonly used on Gas scooters, pocket bikes, mini choppers and all sorts of pit and mini bikes. All ScooterX parts come with a 30 day warranty!