A turbo pad adjuster situated in a Magura HS33 lever. It is the red dial.

A turbo pad adjuster (normally referred to as TPA) is a threaded dial which is situated at the end of the piston in Magura HS33 levers. By turning it, the rider can adjust the engage point of his brakes without using tools, the TPA does this by changing the position of the lever body along the piston. The Magura HS11 do not feature a TPA, however the HS11 pistons can be used with an HS33 lever.

Turbo pad adjuster is a trademark owned by Magura. Note, however, that the Echo CNC rim brake employs a similar technology.