Pipe Coupling/Pipe Socket

https://www.tcpipefittings.com/products/pipe-coupling-pipe-socket/

PIPE COUPLING/PIPE SOCKET
A pipe coupling China, also known as a pipe socket or simply a coupling, is a fitting used in plumbing and piping systems to connect two pipes or tubes of the same diameter together. Couplings are an essential component in the construction and maintenance of pipelines and plumbing systems.