Rust-Oleum 271791 Stop Rust Leak Seal Flexible Rubber Coating Sealant, Black - 2 Pack 2 Pack! Save some money. Exterior/interior use on gutters, roofs, flashing, ductwork, PVC, masonry, concrete and more. High build, oil-based formula seals leaks and cracks instantly Dries to touch in 1 hour and covers up to 40 sq ft Prevents water and moisture penetration for ultimate protection