DIN is an acronym that stands for the German Institute for Standardization, DIN11851 is the German standard for high-profile fittings for use in the wine, dairy, chemical and pharmaceutical industries, for confectionery and food in general. It comprises of a round slotted nut and a flush fitting lipped seal. The male fitting features an inverted cone face that carries the seal, while the liner is similarly conical in section.
It has the distinction of having the swivel on the male as opposed to the screw systems that provide the swivel usually combined with the female. It is widely used in the UK, across Europe and the Middle East and is also fairly widespread in the United States. There are butt welded commercial versions, with adapters for mounting on flexible hoses, elbows, tees and different reductions.