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, whilst keeping the room secure, and the vulnerable protected. It's not only home owners using cable restrictors, they are now being widely used in business premises, and public buildings, such as schools and hospitals to help prevent accidents and maintain security. This keyless restrictor is suitable for use on fire escape windows.