Pipe fittings are components used to connect, control, or redirect the flow of fluids in piping systems. Common types include elbows (to change direction), tees (to join three pipes), couplings (to connect two pipes), reducers (to adjust pipe size), unions (for easy disconnection), caps and plugs (to seal ends), flanges (for bolted connections), nipples (short connectors), and bushings (to reduce pipe size within a fitting). They are made from materials like metal, plastic, or PVC, catering to different applications such as plumbing, industrial, or gas systems.

Common materials include steel (carbon, alloy, stainless), copper, brass, plastics (PVC, CPVC, PEX), and composites.

Pipe fitting size refers to the dimensions of a fitting that determine its compatibility with pipes in a plumbing or piping system. It is typically measured in terms of nominal pipe size (NPS), which indicates the approximate inside diameter, or outer diameter (OD) for some fittings. Sizes are standardized and often range from fractions of an inch to several inches for industrial use. Accurate sizing is essential for proper fit, sealing, and performance in fluid or gas flow applications.