That's the best one I've seen yet!
The tubes may or may not be the right size, but they are unfortunately the wrong type. Lots of people (especially eBay sellers) who don't know any better, call other types of readout tubes “Nixie” tubes when they are not. What you have there are vacuum-fluorescent displays a.k.a. “VFD's”. Nixie tubes have numbers inside that are made of thin silver-colored wire or etched sheet metal. Each number is a complete digit unto itself (not the now-common 7-segment style), and they are stacked on top of each other from the front to the back of the tube. If you have the chance to see them working before buying, Nixies use a mixture containing mostly neon gas so can only light in a narrow color range from pink to orange to red (usually orange). VFD's are usually blue or green.