Brass Compression Tube fittings are used in plumbing to join two tubes or thin-walled pipes together. In instances where two pipes made of dissimilar materials are to be joined, the fittings will also be made of one or more compatible materials appropriate for the connection. Compression fittings for attaching tubing commonly have ferrules in them. Brass compression tube fittings are also used extensively for hot and cold water faucets and toilet stop valves. As the name implies, compression fittings form a tight seal by applying a compressive force to the pipes and pipe fitting. The fitting is compressed against the pipe with a force sufficient to eliminate all space remaining in the joint, thus preventing fluid from leaking. This fitting is composed of an outer compression nut and an inner ring called an 'olive'. When the nut is tightened, it clamps-down on the olive, causing it to conform to the circumference of the pipe. Olives vary in shape and material according to the pipe material. To work properly, the olive must be oriented correctly. Typically the olive is fitted such that the longest sloping face of the olive faces away from the nut. Compression fittings are popular because they do not require soldering, so they are comparatively quick and easy to use. Compression fittings are especially useful in installations that may require occasional disassembly or partial removal for maintenance etc, since these joints can be broken and remade without affecting the integrity of the joint.