These Sioux compression sleeves are designed for use with 3/8" outside diameter tubing. They are made of brass for strength, durability and rust resistance. The compression sleeves are recommended for use with copper, brass, aluminum or plastic tubing. They are typically used on gasoline, grease, oil, water, vacuum and air line applications. The compression sleeves are not recommended for use with steel tubing. The pack includes 3 compression sleeves.