The 6AK5 is an amplifier pentode that is physically small and the electrode assembly is no more than a 10 mm cube. The use of this device lay in low noise RF amplification at VHF. See also5654 special quality version of the 6AK5.
The flat face of the anode with side straps holding the two sides together.
Looking along the axis of the grids through the open end of the anode. All three wire grids can be seen with the suppressor grid a much more open pitch than the inner grids.
The thin glass tube envelope is 18 mm in diameter and excluding the B7G base pins, is 35 mm tall.
References: Datasheet, 3002 & 1040. Type 6AK5 was first introduced in 1942.