A unique feature of the Deluxe Signal Tube is that the diver can fill the tube at depth by holding the open bottom of the tube over a regulator mouthpiece while the regulator is being purged. The air will enter the tube through a large Duck-bill valve at bottom. When the tube is sufficiently filled with air, the diver can release it to the surface (while tied to a line) a built-in Over Pressure Relief Valve allows the tube to ascend without rupturing. This way a diver can signal he will soon be ready for pick-up, without going to the surface immediately. There is also an oral inflate valve for surface use. Measures 7" wide x 60" tall. Develops 22 lbs of lift in fresh water.