Dow Corning Contractors Weatherproofing Sealant (CWS) Medium-modulus silicone joint sealant. Dow Corning Contractors Weatherproofing Sealant (CWS) is a one-part, moisture cure, medium modulus sealant that provides durable, flexible, watertight joints and offers outstanding unprimed adhesion to most non-porous substrates. It is specifically developed for sealing dynamically moving joints. Dow Corning Contractors Weatherproofing Sealant (CWS) used sealing dynamically moving joints such as expansion and control joints, concrete panel joints, tilt-up panel joints, curtainwall joints, perimeter caulking (windows, doors, panels, EIFS, bedding of mullions, panels, and frames, etc.) Color: Gray Contents of Sausage : 20 fl oz (590 ml)