Installation Requirements: 23mm wheel shower door runners, suitable for glass doors with a thickness of 4-6mm. Upper and lower wheels are designed for glass apertures of 12-14mm. The upper wheel can be adjusted up to 8mm using stainless steel screws. The lower wheel spring automatically adjusts based on the upper wheel height. Shower Rollers Materials: 23mm sliding shower door wheels are constructed with copper swing arms and electroplated plastic alloy for durability and strength. Widely Used: Replacement roller runners fit most standard shower enclosures, shower cabins, and steam rooms. Installed at the top and bottom of the shower door to ensure smooth opening and closing operation. Easy to Install and Use: Operates quietly with no noise during use. Designed for smooth sliding performance on glass doors. Simple to install and maintain. Ideal for DIY replacement. Package Includes: Set of 4 single shower door rollers (2 top rollers and 2 bottom rollers). Each set includes 4 bumper blocks and stainless steel screws. Material: Brass, Stainless Steel, Nylon. Strong Load-Bearing Capacity: Features a thick copper shaft for enhanced load support. Ultra Quiet: Integrated ball bearings provide silent, stable, and powerful sliding operation. Stable Performance: Even force distribution on the upper rail ensures smooth push-pull action. Lower rail allows effortless, smooth sliding with safe and reliable operation.