Material: 18 gauge CRS frame and 20 gauge blades. Min size 6″ x 4 Max 48″ x 80″. Construction: Louvers: Inverted “Y” blades with 1″ blade spacing are attached by interlocking construction to the 1″ deep, welded frame. Non-vision. Multiple sections can be combined for larger sizes. 800A1 Frame: Self-attaching frame with 1-1/4″ trim, mitered and welded corners. Screws fasten through frame into louver core, leaving corridor side of frame free of fasteners.