The Camco FasTen Leveling Blocks allow you to stack the interlocking blocks to the desired height for safe and easy leveling. Each block adds a full-inch to stack height. Camco's FasTen Leveling Blocks can be used with single wheels, double wheels, hydraulic jacks, tongue jacks, stabilizer jacks, 5th wheel jacks and tandem axles. The convenient carrying handle easily pulls up for carrying, or twists down to secure blocks together for storage. Stack height should not exceed 4-1/2 inches.