The surface of the connects is made of plastic has strips that are much easier f you to turn. They can be applied repeatedly. The usual size f most bottles is better than other connects (size: 1.3 x 1.9 inches) Use a connect to connect a bottle with about 3/4 water an empty bottle. Shake the bottle hizontally 4-5 times, then the swivel in the bottle rotates Great educational toy f your children, perfect gift f Christmas, birthday other holidays It is a great educational entertaining experiment tool f school classes, home schoolers scouts. It can help to increase children's intelligence awaken children's interest in physics study You can add colour washing powder to the water in the bottle so that the small tnado you create has different colours bubbles, which is me interesting