The Airgas® Y99-GSTD Series steel tube style cylinder support racks are available from single cylinder to eighteen (18) cylinder racks. All support racks are made of heavy, 11-gauge square tube steel construction welded 4 sides at each intersection. All exposed ends are poly capped. Units have welded plated chain with bit snaps at 2 levels per cylinder. All units meet UFC1985, NFPA, UBC, and UL construction requirements. Rated for Seismic Zone 4.