CHiQ 120" S-CK ALR Black Grid Projection Screen (UST)Changhong S CK series ALR (Ambient Light Rejecting) screen is specially designed for UST (ultra short throw) projectors. With the advanced optical lens system, S CK series can efficiently reject ambient light from the ceiling, and present the light from projector only. The lens system consists of multiple layers, each have the property to reflect angular light. The combination of these layers allows the S CK to focus on reflecting projector light.