What are the rules for a table tennis bat?

• Blade: flat and rigid; at least 85% natural wood by thickness. Thin layers of carbon fibre, glass fibre or compressed paper are allowed inside it.
• Covering on a striking side, either:
  • ordinary pimpled rubber, pimples outwards, under 2.05 mm thick in total; or
  • sandwich rubber, a layer of sponge under pimpled rubber with pimples in or out, under 4.05 mm in total.
• Colours: one side black, the other a bright colour plainly different from black and from the ball. Both matt.
• A side left bare may not be used to hit the ball, and must still be black or the bright colour.
• The rubber must be a type currently authorised by the ITTF, with its logo and brand visible near the handle.
• No treatment: the rubber must be used as authorised, with no additives, and glue must not contain harmful solvents.
• Before a match, and whenever a bat is changed, the player must show it to the opponent and the umpire.
• A bat may be replaced during a match only if it is accidentally damaged so badly that it cannot be used.
• At major events a racket control centre tests bats. One that fails before a match cannot be used.

Different rubbers put very different spin on the ball. Two colours let the opponent see which rubber made the shot, and the limits on thickness and treatment stop equipment outrunning skill.