Typically supplied in 16-gauge or 18-gauge steel, hollow metal doors can be made of either cold-rolled steel or A-60 galvannealed for added corrosion resistance.
Edge seams are interlocked with the option to have a filled seam for aesthetics. Core options include honeycomb, polystyrene, polyurethane, steel stiffened and mineral cores.
Additional components to consider for the complete opening are the frames and hardware.