20-40 HRA 45-75 HRA 80-85 HRA It is mainly used to determine the hardness of very hard materials, such as cemented carbide, very thin and hard steel, and hardened materials with a thin surface hardening layer; 20-50 HRB 60-70 HRB 88-100 HRB It is often used to determine low-carbon steel, soft metals, copper alloys, aluminum alloys and malleable iron and other medium and low hardness materials. 20-30 HRC 35-55 HRC 60-65 HRC Mainly used for the determination of general steel, castings with higher hardness, pearlitic malleable iron and quenched + tempered alloy steel and other materials. 60X100.22kg Note: The above models are conventional matching blocks for hardness testers.