I've spent the last few days looking through this Sylvania catalog and the t14.5 tube really surprised me since I didn't think there was anything between t12 and t17.

When were these sold and are these still available?

Interesting. Never knew such existed.

Cool find. It would be nice to see a photo of one sitting between a T12 and T17 tube for size comparison.
I did a similar comparison with my now smashed F40T10 tube.

@xmaslightguy Apparently they're used in some cars...

@108CAM It would be 2.5 bigger than t12 and 2.5 smaller than t17.

Interesting, I'll have to look more into this later. I didn't know a T14.5 fluorescent lamp existed.

For those wondering about the size, North American fluorescent lamp designations are based off the diameter of the tube in 1/8ths of a inch. T12 would be 12/8 of a inch or 1-1/2" diameter (38.1mm). T17 would be 17/8 of a inch or 2-1/8" diameter (53.975 mm). T14.5 would be 14.5/8 > 29/16 inch or 1-13/16" diameter (46.0375 mm).