Chamberlain Garage Door Chain Drive Rail Extension Kit includes rail extensions, a chain and cable, along with all the necessary hardware needed for installation. This kit is designed to be used with Do it private label or Chamberlain garage door operators, ensuring compatibility and reliable performance. Available in different sizes, this extension kit helps extend the reach of your existing garage door chain drive system, making it a convenient solution for longer doors. The package comes neatly boxed for easy handling and storage. Model Number: 7708CB-P