This Sioux flare union is ideal for use with copper, brass, aluminum and welded steel hydraulic tubing that can be flared. It is made of brass for strength, durability and rust resistance. The 45° fitting has a 3/8" flare end and a 3/8" male threaded half union end. The union fitting is designed for high pressure applications and is typically used for gasoline, grease, oil, water, vacuum, air lines, L.P. and natural gas applications. It is not recommended for use with polybutylene or soft plastic tubing.