5R4G/GB/GYB

5R4 rectifiers (any suffix, GY, GA, GB, GYB, etc) are pin compatible with 5Y3, 5U4, 5V4 and 5AR4/GZ34 rectifiers. They produce a similar voltage drop to 5U4 rectifiers but require only 2 amps of heater/filament current from the power transformer as opposed to 3 amps for a 5U4. This makes them good substitutes for the other rectifier types when different output voltage is desired. These are particularly useful in guitar amps that use a 5AR4/GZ34 rectifier as a stock part.

Coke bottle ST shape, brown base.  Labeled Lewis and Kaufman. Received in bulk packaging, sold in white boxes.

Slightly more sag than a 5U4GB. Great option for amps that call for 5AR4/GZ34s where lower plate voltage, more sag/compression, and earlier breakup are desired.

Built like a tank for the military. We call this one the "potato masher".