steel beam arch Spec.: 25U, 29U, 36U Standard:GB/QB Materials: 20MnK, Q275 Length: 8,9,10,12m steel beam archSpec.: 25U, 29U, 36U Standard:GB/QB Materials: 20MnK, Q275 Length: 8,9,10,12mit is mainly used for mining tunnel support ,with the features of high presure long fit strong structure. U type U25/U29/U36 steel beam arch