Standard Features:
- Supply Size: 18"" x 18""
- Return Size: 18"" x 18""
- Galvanized steel provides excellent corrosion resistance and longevity
- Collar installed with expansion lock and then sealed air tight with hot melt glue or parabond aluminum adhesive
- Black diffuser board coated with EPA-registered anti-microbial protective acrylic agent along air stream side
- Sold in sets of one supply and one return
