The GRAV Gravitron – 11″ perfects the highly potent rips of a gravity bong with the first all-glass gravity smoking system. The outer base is designed to be filled with 8″ of water. Once the 12mm funnel bowl is ignited, the inner bottle is slowly lifted (while holding the outer base down), pulling smoke into the inner bottle. Lowering the bottle back down into the outer base forces smoke through the 16mm downstem, which doubles as a mouthpiece when the bowl is removed. Get ready for the big, powerful rips of a DIY Gravity bong with a much cleaner-tasting, flavorful profile.