The 6257 is a 5000 watt, water cooled, triode with a mu of 20 made by Machlett with a maximum frequency of 110 MHz. Its water cooling jacket in integral to the tube's anode structure. The 6226 is the same tube with provision for an external water jacket and the 6258 is the same with a forced air cooled anode. The second example has a different filament cap structure and has the filament and grid clamps attached.
Length = 10.00" Diameter = 2.63"
Max voltage = 5500
Max current = 1.5 amp
Fil voltage = 12.6
Fil current = 29 amps