Aluminum stretcher tubes are lightweight and rustproof. The No. 516 3' Aluminum Stretcher Tube can add up to 4 feet 8 inches of length to your stretcher in 4 inch increments. Crain aluminum tubes feature a score line on the inner tube and the outer tube for aligning the buttons with the holes during length adjustment. These tubes work with other standard size diameter tubes. Closed length: 2 foot 10 ½ inches. Range of useful length adjustment: 3 feet to 4 foot 8 inches.