The diagnostic quick coupling socket with shut-off valve and external NPT thread is designed for precise pressure measurement in hydraulic systems, ensuring reliability and safety in demanding applications. Manufactured in compliance with ISO 15171-1 and SAE J1502 standards, it guarantees full interchangeability with connectors from other leading brands. Permanently installed hardened steel plugs integrate seamlessly into the hydraulic circuit, while the socket, connected via hose to a pressure gauge, enables fast and accurate diagnostics. Both plug and socket feature integrated valves that provide secure, leak-free connections and disconnections, with minimal oil loss of approximately 0.1 ml and air inclusion as low as 0.02 ml, protecting system integrity. Flat sealing surfaces further enhance cleanliness and efficiency, while the robust galvanized steel body and NBR sealing ensure durability under extreme conditions. With a working pressure of 400 bar, burst resistance up to 1300 bar, and reliable performance in vacuum applications up to 0.9 bar, this coupling is engineered for maximum safety. It supports hydraulic oil flow of 4.2 l/min at Δp = 3 bar and operates flawlessly across a wide temperature range from -40°C to +120°C, making it an ideal solution for professional hydraulic diagnostics where precision, durability, and ease of use are essential.