Attention! Before buying any 5AR4, 5U4, GZ33, or GZ37, here is a hot ticket from Uncle Kevvy: Buy the Philips 5R4GYS made in Holland. Click here for info. Very rare. We got a stash of them, and they are incredible. The only thing you have to do it make sure that sure you have enough height clearance... we provide you a picture illustrating the height of them so there's no surprises.
Excellent current production 5U4GB made in Russia. If your amp comes with a 5U4GB, this is usually what manufacturers are using. Solid tube, reliable, and sound great!