Walker "Competition " Air Filter is The direct replacement to your "Red" Airbox for your Sprint Car. Constructed using a rigid foam that keeps the weight and costs down. This is Washable / Re-Useable. High Performance Air filter Box 4" and 6" options available. They replace the competitors box and actually seals to keep dirt out of the engine. This is an 80% filtration improvement over the competition. They have a soft polyurethane sealing surface to ensure complete sealing all the way around the box.