Premium material: The crane wheel is made of excellent 45# steel material, with high strength, good stability, low creep, wear resistance and chemical stability, robust and durable for long-term use. Easy to use: The rotating wheels can be used with ropes or cords indoors or outdoors for flexible sliding. The smooth roller ensures good rope movement. The upper part is fixed and the rope is easy to handle. Practical design: Double roller bearings slide stably and smoothly, making it easy to slide the gate indoors or outdoors for flexible sliding. With compact structure, easy to use. Wide application: Suitable for sliding doors, rail doors, various types of angle iron, angle iron rails, etc. Can be used for home training equipment, exercise equipment and wheel machines. Or wheels for indoor and outdoor ropes, clotheslines, wheels, etc. Package contents: You will receive 4 pieces of U-groove rollers; Widely used in car manufacturing and other automated production lines and various general mechanical equipment.