The 4CX300A or 8167 is a 300 watt tetrode with full ratings to 500 MHz. This tube requires forced air for cooling and was designed for high shock and vibration. The X578 was an experimental stage that Eimac used to limit resonances within the tube. The Y-180 is a special 300A with Nickel-Rhodium plating and the 4CX125C is a horizontally finned version. The second example is an early (1959) tube with a less effective anode ribbon structure. The third example is an Eimac made for the military.
Length = 2.50" Diameter = 1.65"
Max voltage = 2500
Max current = 250 ma
Fil voltage = 6
Fil current = 2.6 to 3.1 amps