Type A - Without gasket
Type AC - With gasket in copper
Type AA - With gasket in aluminium
DIN908 Threaded Plug
The gaskets in types AC and AA correspond to the gaskets DIN 7603, type A (flat gaskets), and are available in aluminium or copper.
Steel ST - Tensile strength class 5.8, ultrasonically and tensile tested, zinc plated, nano-passivated (silver / yellowish)