800 series louver with inverted y blades inverted y blades recommended for schools, class a and institutional buildings with non-vision construction and 4 mounting options 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.