Last-A-Span 1163 Mastic is a durable highly viscous sealer caulk. It has been used to seal pipes, risers, parapet walls and all types of roof obstructions. Last-A-Span 1163 is a superior mastic and recommended for use as a sealer on all roof surfaces. It is highly recommended to seal areas of potential concern and problem areas on buildings before applying TEMP-COAT liquid ceramic insulation. This ceramic Elastomeric sealer is water soluble which makes cleanup of the job site and tools quick and very easy.