The main standards are: 12", 14", 17", 20" Features:1) Standards: GB/T14975-2002, GB/T14976-2002, GB13296-91, GB9948-88, ASTM A312, ASTM A213, ASTM A269, ASTM A5112) Our products are corrosion and high-temperature resistant3) The main standards are: 12",...