A fitting brush is a wire brush made for cleaning the inside of copper fittings. The wire bristles prepare the inside of the fitting to make good contact with the pipe before soldering. Clean fittings and a clean pipe make for a good soldered joint. A fitting brush is a necessary copper soldering tool.
Fitting brushes come in various sizes and styles. Some are single size brushes that come in a standard pipe sizes of 1/2'' and 3/4''. Other fitting brushes are multi-purpose and are made for cleaning the inside and outside of copper tube and fittings in several sizes.