641 Universal Air Filter is the common standard for most aftermarket air filters in kart racing. 

Filter Dimension
• Overall Height: 6.25”
• Overall Width: 4.00” to 3.25” Taper
• Flange Height: 0.625” to 1.00”
• Filter Height: 5.00”
• Flange O.D.: 2.625
• Flange I.D.: 2.375
• Flange/Filter Angle: 10°

This Air Filter fits all 2.5 O.D. Velocity Stacks and Air Filter Adaptor

*Caution! Only clean your air filters with air filter cleaner or soap and water. Anything else may damage your air filter. Let them air-dry overnight. Do NOT under any condition use compressed air, hairdryers, or any heat source to dry filters.