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.