The HK-304L is a 300 watt general purpose triode with a mu of 10 made by paralleling four 75 watt tubes in one envelope. They were used extensively in WWII as pulse tubes and amplifiers. Although they have the same military number as the EIMAC 304TL they differ in the height of the tube so they are not always switchable. All the grid connections came through the glass and were terminated with a metal ring and grid cap. Some had two grid caps. HK also made this tube in the higher mu version the HK-304H.
Length = 8.00" Diameter = 3.56"
Max voltage = 3000
Max current = 1000 ma
Fil voltage = 5 or 10
Fil current = 26 or 13 amps