The most common rectifier tube used in higher powered amps which use a rectifier such as Fender 40 watt and Vox AC-30 amplifiers. Common to higher powered tube amps, like the later Fender Super Reverb amps and the Vox AC30 (or Matchless copies). May be used to replace a 5U4 or 5Y3 and will give a faster more dynamic tonal result. This rectifier has a rise time from 300-400 volts that is about 1/2 that of a 5U4. They work nicely in amps such as the Mesa Rectifier series which use the 5U4. Great if you want a feel and response that is tighter than stock rectifiers yet you want to retain the feel and compression character of a vacuum rectifier over the solid-state setting.  
 
UPC: ECC83