Manual or automatic hardness testing machines, often referred to as; hardness testers, can be applied for a wide range of samples and applications. With hardness testing the type of material and expected hardness will determine test method. Materials such as hardened bearing steels have small grain size and can be measured using the Rockwell scale due to the use of diamond indenters and high PSI loading. Materials such as cast irons and powder metals will need a much larger indenter such as used with Brinell scales. Very small parts or small sections may need to be measured on a microhardness tester using the Vickers or Knoop Scale.