High quality POM plastic construction. Compatible with various shower door types, ensuring smooth and comfortable sliding operation. Designed as a replacement for worn or damaged rollers, this set of four casters helps restore functionality to sliding shower doors without the need for full system replacement. Ideal for use on shower enclosures, bathtub doors, jacuzzi enclosures, and similar applications where smooth door movement is essential. Features fluid bearing technology for effortless opening and closing, with durable wheels that distribute glass weight evenly and control directional movement. Wheel diameter: 20 mm, with 6 mm inner bore, attached using an M4 stainless steel screw. Wheel thickness: 5 mm. Steel wheel core measures 9 mm in diameter and 3 mm in height. Constructed with copper pulley and stainless steel components for enhanced corrosion and rust resistance. Offers stable performance, low friction coefficient, and quiet operation. Includes mounting screws. Suitable for shower doors 4 to 6 mm thick. Easy to install and commonly used for bathroom sliding door rollers.