NuFlex® 110 Butyl Rubber Caulk and Gutter Seal is a single component, “solvent release” butyl, designed to provide excellent exterior weathering properties. NuFlex® 110 is formulated for use on many dissimilar building surfaces. It is our best narrow-bead sealant. Ideal for sealing gutter down spouts, metal storm windows, doors and lap joints. It adheres well to damp surfaces.