1. The chain can bend unidirectionally. It stretches out to open the window and retracts inside when closing the window. 2. Double layer chain is more durable. 3. Equipped with overload protector and can open and close 20000times. 4. Locking force: 2000N. Push/Pull force: 450N 5. Suitable for multiple window types 6. Working speed: 9mm/s 7. Measurements: 420mm x 50mm x 40mm
eBay