RJT Fittings: RJT (Ring Joint Type) is the most widely used union in the UK. The union comprises of a hexagonal nut, weld male, weld liner and a gasket. Wetted parts are 316L stainless steel and the nut is 304. They compromise of an o-ring style gasket which leaves a small crevice where the liner and male part of the union overlap. RJT unions are very popular for frequently dismantled sections of pipework.