Shower Door Rollers,23mm Up or Down Shower Door Wheels, Sliding Shower Door Roller for Enclosure Bathroom Glass Door A set of 4 pieces: 2 rollers for upper shower door + 2 rollers for lower shower door The upper rollers have no buffer spring, you can adjust the position of the wheels by adjustment screws < p>Button rollers with dampening springs for secure mounting Wheel diameter: 23 mm. Suitable for flat sliding shower doors and curved sliding shower doors Constructed of heavy duty zinc alloy, smooth ball bearing and wear resistant nylon wheel