These caps have tapered sides, which offers a close fit. Some of these fittings can be used either as a cap or a plug. Tapered caps and plugs are multi-functional and go well with male and female NPT threads, straight tubes and bars; and male straight threads. These fittings have a tapered body to provide a secure and firm friction fit while facilitating easy removal. The tapered caps are designed to provide protection for all internal and external, threaded and non-threaded fittings against damage, dirt or moisture that can occur.