Our 37 mm - 38 mm angled foam air filter for 125cc-150cc ATVs, dirt bikes, and pit bikes is offered in an eye-catching red color. The 37 mm - 38 mm inside diameter of the rubber fitting is placed on the carburetor. If your dirt bike carburetor has a 37 mm air inlet, which many (if not most) 125cc-150cc carburetors do, these air filters will no doubt fit your dirt bike. Just slip it on, tighten the hose clamp, and your engine is far safer from the dust and crud.Our filters sport a 2-3/4" tall by 3-3/4" diameter foam screen and they include the hose clamp.