Suitable for doors and windows: Ensure the track height is more than 1.5 cm (0.6 inches) and the track thickness does not exceed 1.6 cm (0.63 inches). Not suitable for the middle track of windows. Check your window track before purchasing. Double-opening design: Features an enhanced double-opening mechanism that provides increased friction for a more secure, stable, and reliable lock compared to standard window locks. High-quality materials: Constructed from aluminum alloy for durability and strength. Includes a yellow plastic cover on the key handle for added convenience. Essential safety item: Allows screen windows to remain open during hot weather to improve airflow while using the lock to help prevent accidental falls and unauthorized access. What you receive: 4 sliding window locks with matching keys. Multiple locks can be installed on heavy windows or doors to enhance security.