This Spectre breather filter, also known as a crankcase vent filter, has a flange with an inside diameter of 38mm. By using the included adjustable worm gear clamp, this air filter will fit 1-1/2 inch tubes. Featuring a triple chrome-plated steel construction, this breather filter offers improved flow capacity compared to enclosed element designs. Note: Legal in California only for racing vehicles which may never be used, registered, or licensed for use upon a highway. See spectreperformance.com for CARB status on each part for a specific vehicle. This Spectre breather filter, also known as a crankcase vent filter, has a flange with an inside diameter of 38mm. By using the included adjustable worm gear clamp, this air filter will fit 1-1/2 inch tubes.