CPM Rex 121 is a high vanadium cobalt-bearing tool steel designed to offer the highest combination of wear resistance, attainable hardness, and red hardness available in a high speed steel. Its superior red hardness permits higher cutting speeds compared to other high speed steels. Its superior wear resistance, owing to its high vanadium content, helps to maintain a sharp cutting edge at increased cutting speeds. CPM Rex 121 also bridges the performance gap between high alloy tool steels and carbide materials. It may be used for cutting tools, where high cutting speeds demand higher heat resistance, but carbide is too brittle, or for high wear tooling applications (punches and dies) where carbide tools are too fragile.

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.