Brass 3" Tee. Brass Pipe and Fittings are manufactured for both commercial-industrial and residential standards. Brass has a high level of tolerance, making it ideal for oil, water, and air line applications. Brass fittings are universal, they can be used by professionals and DIY guys. This Brass 3" Tee is the fastest and easiest way to connect your lines. Larger fittings are generally used in areas where durability and quality are demanded.