The STMT 900 MHz Manual Three-Stub Tuner serves for impedance matching and, in connection with a waterload, for realization of reflection coefficients in wide range of the Smith Chart in all subbands of the 900 MHz ISM band. Based on the WR975 (R9) waveguide, the tuner basic design is derived from the HOMER-Series STHT 900-MHz STOLPA Autotuner, with stepper motors substituted by mechanical wheel-and-crank drives. Dials and locking levers serve for repeatable settings.

Although the STMT is equipped with a water cooling system, in most situations, cooling is not actually necessary.