MCNETT SEAMSURE 2 OZ SEALANT WATER PROOFING Seam Sure is a fast drying, water based urethane formula designed for sewn seams on synthetic fabrics and breathable laminates. It has a unique brush tip applicator to work into needle holes, sewn joints, corners, and under lap-felled seams. Seam Sure i Seam Sure is a fast drying, water based urethane formula designed for sewn seams on synthetic fabrics and breathable laminates. It has a unique brush tip applicator to work into needle holes, sewn joints, corners, and under lap-felled seams. Seam Sure is freeze/thaw stable and washable/dry-cleanable. It is ideal for tents, packs, rainwear, garments and tarps. Silnet is specifically formulated for sealing seams in silicone or silicone coated materials.