The codes of grade I steel, grade II steel and grade III steel are HB 235, HRB335 and HRB400, respectively, where H is hot rolled, R is ribbed, and B is reinforced, and the following figures indicate the yield strength in MPa.

Grade I steel is round steel, and others are ribbed steel bars.

The performance of steel bars is clearly expressed upstairs. There is much supplement, and there is little difference in performance between secondary steel and tertiary steel.