Water Cut-Off Mastic is a one-component, low-viscosity, self-wetting, butyl blend mastic designed to be used in conjunction with roofing and waterproofing systems. It is primarily used as a sealing agent between various membranes and applicable when membrane is being terminated using a compression-type seal. Water Cut-Off Mastic is an extremely tacky material and will remain as such when used with compression type terminations.