... :Structure 4)Certification:ISO9001:2000 Hot-dip Galvanized steel pipe 1)Thickness:2.77-6.02mm 2)OD:21. ... , l. Cutting, m. Pickling, n. Inspection.12)Application:Widely used in fire fighting, gas pipes, water transport and water supply ... projects; building, central air-conditioning pipe, fence, threading pipe, rolling doors, metal frame, support tube, furniture, sports equipment, fence, etc ...