This part is a steel component which has been machined by China Turned Parts on our CNC lathes. The component has what is considered a tight internal tolerance of +/-0.02mm and as such an internal reamer was used to machine this part after drilling the initial pilot hole. The black appearance is due to black oxide coating or phosphating. This is an aesthetic coating which oxidises the surface of the metal and dyes the part a black colour in appearance. Generally this is good for appearance but has low corrosion resistance. If a higher corrosion resistance is required then an electoplating such as Black Zinc might be considered. We can also offer the black appearance for stainless steel parts which is more commonly known as ‘stay black’.