9.9FT Sliding Library Ladder Hardware, PU Silent Bottom Wheel with Brake, Carbon Steel Material Rolling Ladder Hardware No harm to Floors and Carpets, MAX Load 300lb **No Ladder ?Mounting Dimensions?9.9ft library ladder hardware Kit includes 3 individual 3.3ft rails and connect seamlessly with rail connectors for smooth sliding. So you can choose to install 1 or 3 3.3ft rails as your like. Library ladder hardware Kit fit up to 1-1/8" thick ladders. The minimum ladder height is the track bracket installation height plus 1". And the bracket widths of the rail is 3 3/8 inches, please make sure the bookcase where you want to install the rail wider than bracket's width ?Mute lower pulley with brake?The lower rollers with brake can secure the ladder from sliding when needed. The wheel part of the lower pulley is made of high-quality polyurethane, which can avoid any damage to your floor and carpet, such as scratching and abrasion. And the internal inlaid refined bearing steel core, which runs smoothly and can effectively reduce the rolling noise ?Safe Dual Pulley Design?The upper rollers of library ladder hardware have a unique dual pulley design. Each upper roller consists of two smaller wheels, which greatly enhances the grip between the wheels and the track, preventing the pulleys from derailing and minimizing the risk of falling. The ends of the track are equipped with rail brakes and end caps, which prevent the pulleys from detaching from the track ends during operation, providing you with a guarantee of safety ?Heavy Duty Carbon Steel Material?9.9FT Rolling library hardware is made of heavy duty carbon steel. The material of connection part has been thickened, while the multi-point fixing is applied between the pulleys and the ladder, which greatly improves the strength of the key parts and ensures a tight and solid connection. In addition, the innovative triangular support structure at the bottom of the rails enhances the overall load-bearing capacity, which can easily withstand 300 pounds of weight