players often used speed glue on their inverted rubber to increase both speed and spin. After the ITTF banned speed glue due to health concerns, manufacturers have employed different methods to create inverted rubber with similar effects of speed glue. These new types of inverted rubber are called tensioned rubber, also called high tension, pre-tensed, or tensor rubber. They come in two types: mechanically tensioned rubber and chemically tensioned rubber. The two types differ mainly in the manufacturing process; mechanically tensioned rubber is made by gluing the rubber topsheet in a vacuum to cause the rubber to expand, and chemically tensioned rubber soaks the bottom foam layer in chemicals that cause the same effect as speed glue on the foam, but lasts longer. Short pips Short pips rubber, also called pips out rubber, is a more controlled attack rubber that provides more speed but less spin to an attack than inverted rubber. Due to the small contact surface with the ball, short pips rubber is not easily affected by the opponent's spin; instead, it will knock a ball away. Therefore, the rubber is usually used for blocking, hitting, and counterattack strokes. Long pips Long pips rubber is a defensive rubber. As its name suggests, the rubber has longer pips than short pips, and usually it also has thinner pips. The flexibility of the pips creates a low friction effect. As a result it provides little spin because the spinning ball slips on the rubber. When provided with a heavy topspin ball from an opponent's rubber, the opponent's spin is returned. However if the opponent sends backspin, the spin is again returned but will be topspin to the opponent which can cause confusion as inverted rubber or short pips rubber would return backspin for the same stroke. This is called "spin reversal" though in fact the spin does not reverse from the point of view of the bystander. The occasion when spin reverses is actually when both players are executing backspin or both executing topspin. Antispin Antispin rubber is a defensive rubber with a smooth surface and very soft sponge. Due to the soft sponge, this rubber dampens speed of the ball and returns the ball at a low speed. It is usually used by defensive players on one side of their racket only. Unlike inverted rubber, it does not grip the ball, so opponents' balls are returned with little spin.