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. A plug is an item that 1 provides a fitted closure for an opening designed to ensure a tight seal such as for a sink or a bottle, or for a hole or a space 2 completes an electrical connection. The plug may be removable as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two points. Features. 0.25 x 0.37 BB Fitting Plug. Made with high quality material