The LaserLine 4-Foot Grade Rod Extension EX provides any LaserLine GR Series Direct Reading Grade Rod with 4 additional feet for measuring. However, with this extension you do not have to add all 4 feet at one time. Instead, you can extend this accessory in 1-foot increments. And when you are not using the extension, it stores away easily by sliding in the bottom of your leveling rod. A 1-year warranty is included.