POM plastic. Adapts to different types of showers. Shower door slides for showers, massage cabins, bathtubs, jacuzzi and even For furniture accessories. Make sure the door or doors open easily and smoothly. Replace your broken system.Top-grade shower rolls Bearing component: Fluid bearing of the door with a slight movement forward or rear effortless for shower cabins, the hydromassage boxes clearly perform the Task assigned to them, distributes the mass of glass, controls the movement in the given direction. This gives the product even more durability and longer life Steel part of the wheel: 9 mm diameter x 3 mm high Type: 4 casters for shower door. Thickness of the wheels: 5 mm. Delivered with screws. Suitable for a shower door of 4 to 6 mm thick. Roller diameter: 20 mm, 6 mm interior hole, attached with a M4 screw. The pulley is made of copper + wheel wheel, and the screw is stainless steel. Steel resistant to the Corrosion and rust, good full performance. Pulley bearing capacity, good stability, small coefficient of friction, good mute effect. Easy installation, often used for bathroom sliding door pulley. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. Sold by-YJL official store