Forming watertight seals, 3M offers permanent adhesion to wood, gelcoat and fiberglass. In addition, this marine adhesive sealant is flexible and allows for structural movement and dissipation of stress that may be caused by vibration, swelling, shrinking or shock. Polyurethane sealants provide strong, flexible durable elastomeric bonds that seal against the elements. These sealants excel in challenging industrial, transportation and construction applications. Polyurethane sealants are available in a wide variety of Shore A hardness, open time and colors to meet many application needs.