The GRAV® Medium Gravitron® is the smaller edition of GRAV's namesake and flagship product, and it's still as much fun and hard-hitting To use the Medium Gravitron, start by filling the outer base with about 8" of water, which should hit just below the decal. Then place the bottle into the base, and load the included 12mm bowl. Place the bowl in the mouthpiece of the bottle, and as you light it slowly pull the bottle upward. The bottle will fill with smoke. When you're ready to hit it, remove the bowl and inhale through the mouthpiece of the bottle as you push it back down into the water. This will create a pressurized flow of smoke that will give you a huge hit in record time. There's a reason the world's first all-glass gravity smoking system is still popular and iconic to this day, and that's that it does the job of delivering big, pressurized hits extremely well.