Package Content: Set of 4 twin shower door rollers (2 pcs top and 2 pcs bottom).(recommended for 14mm glass hole)Galvanized Door Rollers: 23mm (diameter) top and bottom shower door double rollers, surface plated, anti-rust; Suitable for 4-6mm glass door thickness, 12-14mm glass open hole.These Replacement Shower Door Wheels are suitable for most shower enclosures, cabins shower doors and steam cabins, installed at the top and bottom of the shower door, for easy opening and closing.(not fit for dia hole less than 12mm)None sound to open the shower door and these glass shower door rollers help it slide smoothly. It is easy to install and maintain.(recommended for 14mm glass hole).It is recommended to replace the plastic shell shower door sliding roller every six months, and the pulley the metal shell is recommended to be replaced every year.