Precision Tunable shorts are used to provide a variable short circuit reference plane in waveguide set-ups. Each of these tunable shorts consists of a flanged section of straight waveguide with a micrometer driven short attached to one end. The micrometer drive provides precise movement of the shorting plunger of more than one half wavelength at the lowest operating frequency of each waveguide size. The micrometers used on these shorts utilize a special dampening feature making the locking type of micrometer unnecessary. Tunable Shorts are available in sizes WR3 to WR42. Sizes WR3 to WR12 are electroformed, WR15 and above are made from extruded copper. This product is now available with a metric micrometer drive assembly.