9″ Band Spring Box Assembly Zinc Finish with Nylon Bearings | 4-Pack

The 9″ Spring Box Assembly helps lift and balance the door curtain in band spring rolling door systems. It works as a compact counterbalance unit inside the door housing. This spring box is made from heavy-duty galvanized steel for corrosion resistance and long-term durability. It is designed to house a high-strength flat spring and uses nylon roller bearings for smooth rotation around a stationary steel shaft. Spring is sold separately. As the door operates, the spring box stores and releases spring tension. This helps reduce operating force and supports smooth, reliable door movement. This spring box assembly has 8.66″ outside diameter and 2.375″ inside diameter and accepts spring up to 60 mm wide. Package Note*: Sold as a 4-piece package. Price shown is per package.