The brass and copper fittings are made of AISI C28000 brass. The inside thread is BSP 1/2”. The outside surface is knurled. They are brass screw caps. They are also can be made of copper. The color of brass is yellow, and the color of copper is a little red. The brass and copper fittings are made by CNC turning the round brass bar. The overall surface roughness is Ra 1.6, and can be better to Ra 0.8 or Ra 0.4 on demand.