This pencil triode has planar electrodes with very small spacing between them. This reduces electron transit time between them, thus allowing the triode to operate at the upper end of the UHF band (3 GHz). The valve was mounted with coaxial cylinders, whose length determined the frequency of operation
The planar construction was also employed in similar valves used in field gun shell fuses, so they could withstand extreme g forces as the shell accelerated in the gun barrel.