Custom Boat Tube Brownie’s oval shaped “Boat tube” is designed to support the Third Lung system with a very low center of gravity providing maximum stability. Even a visual measurement of the intelligently designed THIRD LUNG center-of-gravity compared to other “top-heavy” systems on the market today will once again confirm the Brownie’s design team actually use their systems in open ocean environments, and re-design until optimized. The construction of the tube assembly begins with a radio frequency-welded inner bladder made of inflatable boat materials and large bore boat type air valve for reliable inflation and rapid deflation/storage (ever try to deflate a tire tube after a great day of diving?). The outer cover is made from rugged woven marine fabrics and double stitched with nylon webbing tape overlaid at every fabric panel joint. Since 1969, Brownie’s Yellow and Red has allowed boaters to see you from a distance. Please join the Brownie’s “Triple B” early season dealer program and help us, help you build a new revenue stream with the THIRD LUNG dive system.