The S2 SORBER is a 22-inch by 24-inch section of encased fiberglass that can be used on the lower half of the CSP to cut reflections, or used as wall treatment for studios, basements, church sanctuaries, etc. S2 units can be applied to the ClearSonic Panels using velcro patches that are included. All SORBER products have a Class A fire rating. Color is dark gray (light gray also available). CLE-S2 are sold in individual sections so you can buy just the right amount for your sound shield needs.