The ball (femoral) and socket (acetabular) components of a BHR are made of a tried and tested alloy of cobalt and chromium. This has been in use in orthopaedic surgery for over 70 years. The original alloy is an as-cast high-carbon alloy. The higher carbon content precipitates in the alloy as carbides which have the hardness of ceramics. They give the metal the needed resistance to wear. These carbides can be depleted by heat treatments in the later stages of manufacture – a process that is used in some other brands of resurfacings. They no longer enjoy the same wear resistance as an as-cast device such as the BHR.