Improved Double Glazed Locks - Double glazed locks can be applied to heavy doors or windows for added security. And it will be more solid, solid and sturdy, exquisite workmanship, aluminum alloy frame and stainless steel screws which can be reused for many times. Quantity and size - double sliding window locks with 4 keys approximate volume 6 x 2.4x 2.4cm , apply track heights above 1.2cm / 0.47inch, thickness of the track not over 1.6cm / 0.63 inch (not applicable to middle track) window, please check your window track before purchasing). Easy to install - there is no need to install any additional tools, it has a hex key in each window lock, held by a key control on the track. Designed for horizontal/vertical windows and sliding glass doors Not for plastic window frames. Wide use - can be easily applied to most environments Keeping windows partially open and closed locks and thieves can prevent children from falling and protect the safety of their families while improving air circulation. Product Guarantee and Customer Service - We do not sell perfect images but products we provide full refund or free reship new products for free if you are not satisfied with our products.