CPM Rex 66 is a super high speed steel made by the Crucible Particle Metallurgy (CPM) process. It is a tungsten type high speed with a high vanadium content for excellent abrasion resistance, similar to that of CPM Rex T15, and 8% cobalt for a higher red hardness than CPM Rex T15. It also offers high compressive strength due to its high attainable hardness. It is best suited for applications requiring both a high red hardness and high wear resistance.

The CPM process results in a homogeneous microstructure with a finer, more uniform carbide distribution imparting superior dimensional stability, grindability and toughness when compared to steels produced by conventional processes. The CPM process also allows the design of more highly alloyed grades which cannot be produced by conventional steelmaking.