2" (51mm) heavy-duty galvanized steel Assembled on brackets or continuous angles Torsion or extension springs counterbalancing Double end hinges are recommended for doors 13’ (3963 mm) wide and more (optional). Horizontal 2 1/2" (64 mm) door reinforcements struts for doors 14’ (4267 mm) wide and more are standards   Standard lift Low headroom (LHR) Low headroom (LHR) with torsion in front Extension 9-1/2" (241mm) 5" (127mm) n.a. Torsion 12" (305mm) 5" (127mm) Rear Torsion 8" (203mm) Front Torsion   Add 2" (51mm) for an electric door opener PVC weatherstrip Artic grade available in white, brown, clay, sand and ivory Nylon roller Quiet and durable Barlock