The 254W is a 100 watt dissipation triode with a mu of 25 with a frequency of 175 MHz for full output. The HK-254 was the original tube that was copied by many others. The 254W tubes are rated at a higher plate voltage. The first example is a PL-254W made by Penta Labs. The second was made by Eimac after they acquiring Penta Labs and continued their product line. The third is marked as a 254W but was made by the Vacuum Tube Prod. Co.
Length = 7.13" Diameter = 2.62"
Max voltage = 4000
Max current = 225 ma
Fil voltage = 5
Fil current = 7.5 amps