The performer displays a bottle and a length of rope. The end of the rope is introduced in the mouth of the bottle, then the other end lifted up. The rope comes away as one would normally expect.
The rope is again placed into the bottle, and a magic pass made. Now the bottle is picked up and inverted, but the end of the rope stays inside the bottle without falling out. You hold the other other of the rope and drop the bottle, and it swings at the end of the rope like a pendulum. Place the bottle down and lift away the rope, and it once again comes free as you would expect.
Anti-Gravity Bottle comes to you complete with the special bottle, rope, and full working instructions.