The letters on the steel bars are registered factory names or trademarks. The first number on the steel bar represents the grade of the steel bar. For example, 3 represents grade 2 steel, 4 represents grade 3 steel, and 5 represents grade 4 steel. The last two digits represent the specification of the steel bar, and the letters between the grade and specification represent the steel bar manufacturer.

The steel bar grade is represented by Arabic numerals or Arabic numerals plus English letters. HRB335, HRB400 and HRB500 are represented by 3, 4 and 5 respectively. HRBF335, HRBF400 and HRBF500 are represented by C3, C4 and C5 respectively. The factory name starts with the Chinese pinyin. The nominal diameter in millimeters is expressed in Arabic numerals.

For example, the letters and numbers on the steel bars are: 4/PG/25. These are the basic information of steel bars, equivalent to ID card information.

The steel factory that represents the third-grade steel (HRB400) code PG usually has the first pinyin, which may be the factory name or the brand; and then the nominal diameter is 25.

To understand it together, it is the HRB400 steel with a nominal size of 25mm produced by PG - the translation is the third-grade steel with a nominal size of 25mm produced by PG Steel.