Two bottles and two cylinders are shown. One of each is handed over to a spectator, while magician keeps the other set.
The magician instructs the spectator to follow his moves exactly. The cylinder is placed over the bottle, held between the two hands and turned over a number of times. When the magician lifts his cylinder, his bottle is always right side up and spectator finds his upside down.
This can be repeated several times much to the delight of the audience.
The booklet 7 By Rick Bronson by David Acer contains a brilliant comedy routine for these bottles.