The SMS (Swedish metric standard) system is designed for applications that do not require regular disassembly of hoses. It consists of an internally threaded ring that has a captive seal designed to provide a smooth, crevice free internal bore. The tightness of this fitting system is guaranteed by the captive seal inserted into the groove on the female which is pressed by the male mating part.
It is a specific type of fitting used especially in the food industry (particularly for the processing of milk), but also used with success in the chemical industry. Quick Coupling: manual tightening is sufficient to maintain a liquid-tight seal. Nevertheless it is advisable to tighten with a wrench to ensure a more solid contact between the various components.