This product is a 2-wheel trolley assembly, which is made of durable galvanized iron material, with good texture, safe and practical. Easy to install and use, it can be easily applied to your door, a very practical accessory that will meet your needs well. Features -Color:Multi -Material:Galvanized iron -Size:9.70X4.10X3.40cm/3.81X1.61X1.34in Aperture: 9mm Maximum load: 50kg - Smooth rotation, can bear up to 50kg. Bearing welding positioning to ensure the stability of work. - Easy installation and smooth corners , anti-rust, suitable for various outdoor environments. - Middle support, high strength, impact resistance. Galvanized iron, anti-rust to use. - Galvanized iron to provide smooth opening/closing evenly in the long term. - Stable characteristics, high performance and in great reliability, simple, easy to install. Package list: 4 x rollers