I don't believe there's anything larger than the MASSIVE Rodan CD-47 NixieTubes from Okaya Electric Co. Japan.
The tubes themselves stand over eight inches tall, with digits approximately6 inches tall. They'll light a room nicely.

The NixZilla clock is based entirely on the GPSII clock electronicspackage. The GPSII  HV power supply was modified 
to deliver a whopping 150 ma at 180vdc using a SEPIC circuit. That'sa lot of juice. Those CD-47's require 25ma per tube.
 

The six tubes are arranged parallel on a section of extrusion stock,with the clock electronics hidden inside. Colon posts are clear acrylic.
Three clocks were assembled. Two were presented as gifts. My spouseasked that I take my personal NixZilla clock back to the office.

I will be taking some images of the clock shortly. The only image onfile is the original prototype spread across a desk back in late 2002.

And for you tossers: the name "NixZilla" has been in use since 2002 to describe this giant clock.
Recently, I've seen no less than three individuals using NixZilla to describe their homebew clock,
and to market smaller B7971 nixie tubes on epay. Imitation is the sincerest form of nothing dude.

 
 
 These Rodan CD47 / GR-414 tubes are extremely scarce, and highly sought after by collectors.

Do you want to assemble your own giant nixie tube clock?

You can purchase my spare set of six tubes for sale. These tubes are new old stock, in their original boxes.
Five tubes are in their original boxes, and one has no box. $5000.00 USD  My price is firm, no trades.

 
 
 Click on the small image above for a larger view of the tubes.

You can find my contact information on the page link below.
 

ClickHere to return to the Nixie Clock and Nixie Wristwatch site