XIANQI Material: Nylon Copper, Good Elasticity, Good wear resistan, corrosion resistance, rust prevention, of stable quality and has a long service life.Shower Door Rollers Size: Diameter of the wheel: 20mm; wheel thickness: 5.5mm. Suitable for 4-6 mm glass thickness. Total length: approx. 33 mm. For Glass Door Openings:10~12mm; 12mm recommended. Thickness: 4-6 mm. DIY replacement: It is easy and convenient for this door knob DIY replacement; you can simply disassemble it by screwdriver and replace with new rollers on glass doors. No Noise to open the shower door and these glass door roller help it slide smoothly. It is easy to Install and Maintenance. Installed on the top and bottom of shower door, to make it easy to open and close.Wide Application: For shower doors and massage cabins, bathtubs, Jacuzzi or any other furniture fittings. Suitable for most Shower Enclosures, Shower Cabins and Steam Cabin Enclosures. Package Include: Set of 8 rollers. Over time, the rollers need to be replaced. A Perfect Spare/Replacement.