Unique One - Piece Housing The smooth one - piece sealed housing, constructed of heat - resistant cross - linked polyethylene (XLPE), features our patent - pending filter - to - housing interface. Its innovative design minimizes the total number of parts, making for an easy installation. A large, clear sight window allows for hassle - free filter inspection, without having to disassemble your system. It directly attaches to the vehicle's existing air inlet and features an additional auxiliary air inlet that can be used to bring in additional air.