Moeller #032612 rotationally molded, cross linked polyethylene plastic. The fittings hold the highest OD and ID tolerances in the industry, ensuring you the highest level on input f;low. Machined aluminum 3/8" withdrawl fittings have 360 degree rotational capability for hook up convenience. Conforms to al ABYC, NMMA and USCG regulations. Add 2 1/8" to tank height dimension to accomodate fill hieght.