This tube is more than 9″ (23 cm) tall. Maximum plate dissipation is 1000 watts. Max plate voltage rating is 30,000 volts. The 4PR1000B is pulse rated version of its cousin the 4-1000A.
Filament takes about 21 amperes at 7.5 volts. Filament power alone is so high that you can damage the glass seals if you operate it without forced air cooling