Improved Double Glazed Locks - Double glazed locks can be applied to heavy doors or windows for added security. These locks are solid, sturdy, and feature excellent workmanship with an aluminum alloy frame and stainless steel screws that can be reused multiple times. Quantity and Size - Includes 4 double sliding window locks. Each lock measures approximately 6 x 2.54 x 2.4 cm / 2.36 x 0.95 x 0.95 inches (LWH). Designed for track heights greater than 1.2 cm / 0.47 inches and glass thickness of 1.6 cm / 0.63 inches. Not suitable for middle tracks or top tracks. Please measure your window track before purchasing. Easy to Install - No additional tools required. Each lock comes with a hexagonal key for installation and operation. Secured via key control on the track. Designed for use with horizontal or vertical sliding windows and glass doors. Not recommended for plastic window frames. Wide Application - Suitable for various environments. Allows windows to be securely held in a partially open position, improving air circulation while preventing unauthorized access. Helps prevent children from falling and enhances home safety. Product Guarantee and Customer Service - We offer a full refund or free replacement for any dissatisfaction with our product. Our focus is on delivering reliable, high-quality items.