Features: The wheels are made of nylon, and the center bearing is made of solid-copper. Fully enclosed bearing, waterproof and dust-proof, strong load-bearing. Suitable Glass Thickness: 4-6mm/0.16-0.24inch.Easy to install and maintenance. They adjust-able up and down to allow the door to be lined up to mate with the frames. When you slide the door, there is no noise and slide smoothly. Suitable for Most Shower Enclosures, Shower Cabins Enclosures. Specifications: Material: Nylon Wheel Diameter: 27mm (1.06inch)/25mm (0.98inch)/23mm (0.90inch)/20mm (0.79inch) Suitable Glass Thickness: 4-6mm/0.16-0.24inch Suitable Opening Size of Glass Door: 10-12mm/0.39-0.47inch Note: Notes: Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1x Pulley