Z-Bar Stiffener Intermediate Reinforcement Description The Z-Bar Stiffener is an intermediate reinforcement for a rectangular duct that is roll-formed from 24-gauge galvanized steel. Classification conforms to a SMACNA “H” equivalent. Special Characteristics Cost-Effective Lightweight Intermediate reinforcement for rectangular duct Related Resources To view all related resources you must log in or request access. Safety Data Sheets Galvanized Metal SDS MDS Sheet