Made of high-quality steel with premiu. M nylon roller wheel and Gcr15 roller bearing, the surface is black matte, High strength industrial grade tracks and pulleys can easily hold 220lbs loads, anti-corrosion and anti-rust. Maintains its beauty and longevity for many years. Ow to choose a si. You can choose the appropriate track based on the width of the door and doorway width. [Fits 29-1/242-1/8 Doorway Width]. Adapt to door thickness: 1-1/5″ to 1-3/4″, less than 21 Wide. 4FT Sliding Door Hardware Kit fits maximum SINGLE Door leaf width:21. The minimum distance from the top of the door to the ceiling is 6. [Fits 42-1/8"-72-4/5"Doorway Width]. Adapt to door panel thickness: 1-1/5″ to 1-3/4″. 6.6FT Sliding Door Hardware Kit for 4 door leaves fits maximum SINGLE Door leaf width:18-1/2. Warning: To ensure that the door can be fully opened and closed, the distance from the door edge to the hole of the door hangers is 1-2/5. The door shaft should be perpendicular to the hole of the mounting hangers. Attached with the most detailed product installation and operation instructions. And detailed graphical marking and measurement methods. You can install it by yourself. [Smoothly & Reduce Noise & Space Saving]. Push and Pull the door very smoothly and effortlessly. Door stoppers with integrated spring, reduces vibration for quiet closing, door floor guide protects your door and No punching on the ground. Save space for opening and closing doors. Suitable for interior door in kitchen, bedroom, dressing room, laundry room, utility room, entertainment console, club, pub and so on. [Package & Professonal Customer Service]. Package Included: Spliced rails with accessories, 4x Hanging Pulley with accessories, 6 door hinge, 2 rotating shaft, all hardware needed for bi-folding door. We provide 724hrs customer service, if your item arrives defectived, we will send replacement at no charge for missing/defect parts. Any questions please tell us, Our customer service will help you within 24 hours.