Upgraded double-glazed lock - the double-glazed lock can be applied to heavy doors and windows for added security. It will be stronger, stronger and with exquisite workmanship, aluminum alloy frame and stainless steel screws can be reused for many times Quantity and dimensions - double sliding window lock with 4 keys ; Volume is approximately 6 x 2.54 x 2.4cm 2.36 x 0.95 x 0.95inch (lwh) for rail height over 1.2cm 0.47inch and thickness of rail no longer than 1.6cm 0.63inch (not suitable for middle rails) windows, please check window rails before purchasing) Easy to install - it is not necessary to install other tools, there is a hex key in each door lock, which is held by a key control on the rail. Designed for horizontal vertical windows and sliding glass doors; Not suitable for plastic window frames Widely used - can be easily applied to most environments; By keeping windows partially open and closed, Anti-Theft and Thief prevents children from falling and protects families while improving air circulation.