The diagnostic quick coupling socket with shut-off valve and internal NPT thread is a reliable solution for precise pressure measurement in hydraulic systems. Designed in compliance with ISO 15171-1 and SAE J1502 standards, it guarantees full interchangeability with connectors from other manufacturers, ensuring flexibility and compatibility. Permanently mounted hardened steel plugs integrate seamlessly into the hydraulic circuit, while the sockets connect via hose to a pressure gauge, enabling fast and efficient diagnostics. The coupling process should only be performed when the system is inactive or under minimal pressure, ensuring safety and durability. Both socket and plug are equipped with advanced valves that deliver leak-free connection and disconnection, while flat sealing surfaces reduce oil loss to just 0.1 ml and limit air inclusion to only 0.02 ml, safeguarding system performance. With a working pressure of 400 bar, burst pressure of 1300 bar, and vacuum resistance up to 0.9 bar, the socket offers outstanding reliability even in demanding conditions. The flow rate of 4.2 l/min at Δp = 3 bar ensures efficient operation, while the robust galvanized steel construction with NBR sealing provides long-lasting resistance to wear, corrosion, and extreme temperatures ranging from -40°C to +120°C. This makes the coupling socket an essential component for professionals seeking precision, safety, and durability in hydraulic diagnostics.