In table tennis equipment, what is the name for rubber with its pimples facing inward?

In table tennis equipment, rubber with its pimples facing inward is called inverted rubber.

Inverted rubber has a smooth outer playing surface, while the small pimples that connect the rubber to its sponge face inward toward the blade. It is the most widely used rubber type among attacking and all-round players because its smooth surface can generate substantial topspin, backspin, and sidespin.

The term can be confusing because the pimples are still part of the rubber, but they are not visible on the contact surface. With short-pimple or long-pimple rubber, the pimples face outward and directly touch the ball. Anti-spin rubber is another outward-facing design with a particularly slick surface and reduced sensitivity to incoming spin.

A racket may use different rubber types on its two sides. Players choose the combination to create contrasting speed, spin, and control, and approved coverings must meet the rules of the International Table Tennis Federation.