ADJUSTABLE WINDOW GAP SIZE: With the SAFELON Window Restrictor, you can choose from two different window opening sizes: 3.62" (9.2cm) and 5.31" (13.5cm). The adjustable window slit size can meet daily ventilation requirements and more customers' needs. Material: The window lock is made of polyamide material, which is strong enough. Rest assured, it can prevent children from playing with windows, pinching fingers; preventing children from falling from windows, etc. Not only for babies but also for pets. Easy Lock and Unlock: Press the double button to unlock, the window can be opened or closed freely. The lock installed has no keys or other missing parts. Adjust the window gap by pressing and holding the slider button on the rod and pushing or pulling the window. It is easy for adults to use, but difficult for babies. EASY INSTALLATION AND TIPS: SAFELON window stoppers provide tape and screws for customer installation.