LOCTITE^® 661 is a yellow/amber, high-strength retaining compound for bonding cylindrical fitting parts, particularly where strength at elevated temperatures is required. It's typically used for holding gears and sprockets onto gearbox shafts and rotors on electric motor shafts. This low viscosity urethane methacrylate acrylic liquid cures when confined in the absence of air between close-fitting metal surfaces or when exposed to UV light of sufficient intensity. It’s designed to prevent loosening and leakage from shock and vibration.