The 4W300B or 8249 is a 300 watt, water cooled, tetrode with full ratings to 500 MHz. The first 4W300B tubes were glass insulated (about 1954-55). This is the smallest EIMAC water cooled tube. The first example features the simple tubes for cooling. The second shows the threaded fixtures that would be used on all future tubes. The Y248 is the same tube with the cooling fixures out the side.
Length = 3.58" Diameter = 1.56"
Max voltage = 2000
Max current = 250 ma
Fil voltage = 6
Fil current = 2.1 amps