R2/SG2 is Takefu Special Steel Company’s steel and HRC is 65 – 64. Blade has razor sharp cutting edge and good retention Sukenari is known for ZDP189 and making knives for Hitachi Steel Company. However, ZDP189 is priced very high and it is not easy to purchase by everyone. Instead, RE/SG series is reasonable despite of it quality. There are 2 types. One is 3 Layer model, and the other is Damascus Mirror Finish. It looks stunning and blade quality is one of the top.