Aluminum Glass Door model 521 is a sectional aluminum door appropriate for environments where maximum light infiltration and/or visual access is required. Designed to fit openings up to 26’11” (8204 mm) wide and 20’1″ (6121 mm) high, the Model 521 features a wide, 2-11/16″ (68 mm) center stile, 3-3/4″ (95 mm) or 4-1/2″ (114 mm) bottom rail, based on door size.