These tubes have a 3" inside diameter and unique design that permits telescoping from fully closed 28" length to fully extended 50" length. With the new "twist-off" screw cap, a simple clockwise quarter-turn locks the tube at the desired length. Tubes are designed for anything that can be rolled. Perfect for protecting charts, maps, blueprints, posters, etc. against creases, bends, tears and folds. Fully adjustable shoulder strap provides convenient portability. Strap and mounting can be removed for storage.