Synko® Pro Set 90 Coverage: Approx. 440 sq. ft. per bag. Setting Time: Approx. 90 minutes. Application: As an Interior/Exterior joint compound, a laminating agent, as well as filling, smoothing and finishing concrete ceilings. Synko® Pro Set 90 is a lightweight compound that sands as easily as ready-mixed all-purpose joint compound. It can be used to bond gypsum boards or to sound-deadening boards together. Pro Set 90 is also safe to use, as a finishing product, on exterior ceiling gypsum boards. Data Sheet