Shower Door Rollers, Lance Home Set Of 8 Single Shower Door Runners / Wheels / Pulleys / Guides 23mm Diameter Home Bathroom DIY Replacement Parts(4 Upper Rollers and 4 Bottom Rollers) 1. Set of 8 Pcs Single Shower Door Rollers (4 upper rollers and 4 bottom rollers). 2. Material: Plastic, Nylon, A Plastic, Nylon BS and stainless steel. 3. Diameter of the wheel: 23mm; Width of the wheel: 6mm. Minimum Hole size in the glass: 11mm. Maximum glass thickness: 6mm. 4. These single shower door rollers fit glass shower doors where the distance from the center of the hole to edge of glass is 18mm. 5. Comes with screw cover caps. Spring loaded action can also fit curved showers. Designed with a nut and a plastic cover.