The Aeroflow Performance line of premium quality weld-in bungs is CNC machined from solid aluminum billet (6061), CS1030 steel or 316 Stainless Steel. These metric weld on fittings have a machined flat surface for the perfect washer seal. Applications include but are not limited to oil or fuel tanks, radiators, valve covers, manifolds and rear axle housings. It is perfect for all your fabrication requirements in any project you dream of.