A compression fitting is comprised of a sleeve, a nut, and the fitting body itself. The sleeve acts as the seal when the nut compresses it into the fitting body. Compression fittings are used in plumbing and electrical conduit systems to join two tubes or thinwalled pipes together. In instances where two pipes made of dissimilar materials are to be joined most commonly PVC and copper, the fittings will be made of one or more compatible materials appropriate for the connection. Compression fittings for attaching tubing piping commonly have ferrules. A fitting is any machine component, piping or tubing part that can attach or connect two or more larger parts. Examples are couplings, compression fittings, and piping and plumbing fittings. Features. 0.5 in. 90 deg Compression Fitting. Made with high quality materialSpecifications. Height 1.45 in / 3.68 cm. Width 8.5 in / 21.59 cm. Length 5 in / 12.70 cm. Size 0.5 in.