Simple and effective twist-lock restrictor for limiting window opening when locked, and full opening when unlocked. Designed for ease of operation and manufactured using high-quality materials, these safety restrictors take just minutes to fit. Allow windows to be opened for ventilation while keeping the room secure and the vulnerable protected. Suitable for use on fire escape windows. Features simple twist operation, keyless locking, quick and easy fitting, high versatility for all windows and doors, and is exceptionally strong, withstanding forces over 1000N.