... 1)Hex head Black oxide high tensile steel bolts 2)Material:carbon ... client require 1) Hex head Black oxide high tensile steel bolts use: Apply to railway and ... High-rise civil building,tower mast structure,lifting machinery and other steel structure ,etc. HANGZHOU RONGLI STANDARD FASTENER ... highway bridge,bolier steel structure,industrial workshop,high-rise civil building,tower Mast structure,lifting ...