Derailing-proof patented Vertical Smart System (US Patent #7, 647, 729) - always keeps wheels in the tracks and ensures smooth and nearly silent operation. No more problems with panels sliding off the tracks. Quick & Easy Set-up: Bottom Tracks installed with silicone glue, no drilling into your floor. Transform your space fast. Uneven floors adaptability - vertical adjustability for up to ¼” to accommodate uneven floors, with a total tolerance of ½”. Sliding Glass Door Complete System includes -