1.ISO9001:2008 2.ASTM A36 steel grade 3.8 types by welding or bolts 4.Galvanized or Untreated 1. Sinosteel Steel Stair Tread TypesT1: Welded fixing, banded ends, no nosingT2: Bolted fixing, holed end plates, no nosingT3: Welded fixing, banded ends, checkered plate nosingT4: Bolted fixing, holed end plates, checkered plate nosing1.5 Welded fixing, banded ends, nonslip nosing1.6 Bolted fixing, ...