NOTICE: Be sure to enter the Make & Model of component you are purchasing tubes for. Failure to do so will delay processing of your order. This does not imply that we confirm compatibility. Consult the manufacturer and owner's manual before ordering.
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.
Now: On to the Mullard GZ37: In original military boxes made in the 1960's. Similar to the GZ33, but the net result with be a small drop in plate voltage to your power tubes and perhaps a slightly softer top and bottom.