5U4 tubes

Anyone know what 5U4 tubes are used for? I was digging through my tubes and found them. Funny how things turn up I don't recall ever having.

I think that that is a power rectifier tube.
YES- It's a rectifier.
Is there something in current production that would use this tube? Just trying to find out if they are wroth anything. They appear to be in excellent condition.

Yes, a number of current pieces use it. It's related to the GZ37. Check out www.tubeworld.com for more info.
Thanks Rpf
The 5U4 are used in alot of tube testers.
Look here.