Dual cure, acrylic dimethacrylate ester fluorescent threadlocker designed for the permanent locking and sealing of threaded fasteners.LOCTITE 263 is a red, dual cure, acrylic dimethacrylate ester fluorescent threadlocker designed for the permanent locking and sealing of threaded fasteners. It cures between close fitting metal surfaces and prevents loosening and leakage from shock and vibration. It works on active metals (e.g. brass, copper) and passive substrates such as stainless steel and plated surfaces.