Package Content: Set of 4 twin shower door rollers (2 pieces top and 2 pieces bottom).(Recommended for 14mm glass hole) Galvanized Door Rollers: Twin shower door rollers top and bottom 23mm (diameter), plated surface, 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, shower cabins and steam cabins, installed at the top and bottom of the shower door, for easy opening and closing.(Not fit for hole dia less than 12mm) No noise 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 Rollers every six months, and the metal shell pulley is recommended to replace it every year.