This Sioux brass flare coupling 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 fitting features a 1/4" compression end and a 3/8" fine-thread female flare end. The pipe 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.