Because of TiN's metallic gold color, it is used to coat costume jewelry and automotive trim for decorative purposes. TiN is also widely used as a top-layer coating, usually with nickel (Ni) or chromium (Cr) plated substrates, on consumer plumbing fixtures and door hardware. As a coating it is used in aerospace and military applications and to protect the sliding surfaces of suspension forks of bicycles and motorcycles as well as the shock shafts of radio controlled cars. TiN is also used as a protective coating on the moving parts of many rifles and semi automatic firearms, as its extremely durable. As well as being durable, it's also extremely smooth making removing the carbon build up extremely easy. TiN is non-toxic, meets FDA guidelines and has seen use in medical devices such as scalpel blades and orthopedic bone saw blades where sharpness and edge retention are important. TiN coatings have also been used in implanted prostheses (especially hip replacement implants) and other medical implants.