SCHERTLER professional tuners for classical guitars with or
  without the bearing design with EBONY KNOBS
  SCHERTLER open-gear tuners are made for 3-left/3-right
  headstocks. They are precisely engineered in a compact zinc case
  and worm shaft in steel, with an 18:1 gear ratio and adjustable
  knob tension. The result is a smooth and accurate performance.
  The TBR PRO model offers a low-friction roller bearing design and
  an aluminum shaft body. The TBR PRO tuners are lighter and the
  design allows free movement of the shaft without friction while
  tuning the guitar, providing a super-smooth tuning experience,
  increased durability and no roller wear.
  All models feature genuine polished ebony fitted or metal knobs,
  with brass internal shaft bushings for durability, and
  eye-catching unplated brass crown gears.