4YH25 steel bar, "4" represents the steel bar grade HRB400; "YH" represents the factory name (or trademark), and the YH steel bar manufacturer code is such as: Jiangsu Yuhua, Xinyu Iron and Steel, Changbaishan (Tonghua Steel); "25 ” means the nominal diameter is 25mm.

Reference: GB1499.2-2007 "Steel for Reinforced Concrete Part 2 Hot-rolled Ribbed Steel Bars"