Made of high quality zinc alloy and nylon, this shower door pulley is durable. Wear-resistant nylon rollers and ball bearings make it easy to use. Contains 4 shower door pulleys, 2 upper pulleys and 2 lower pulleys. The upper roller has no spring and the roller can be adjusted by turning the screw. The bottom roller has a built-in buffer spring to fix the inside of the card slot. The diameter of the roller is about 23mm, suitable for glass doors with a thickness of about 4-8mm. For better installation, the diameter of the glass opening should be greater than 12mm. < p>The distance between the opening of the upper wheel and the top of the glass is less than 12 mm. A shower door requires 4 rollers, it is recommended to replace them in pairs.< /p> When installing, install the upper roller first, then install the lower roller.