T8 or T5?

[Imakesigns]

I will be putting up a sign on an old wall mount with 8' bulbs. He wants to replace the bulbs (story goes the fixture still works...) I got this picture and that's all I have to go by. Visually I would call it a T12. Could it be T8? Anyone have any input?

 

[dasigndr]

it would say right on the lamp if it is T12 or T8

 

[JBurton]

Or you could measure them. T values on lamps is a 1/8" increment. So a T12 is 1.5", T8 is 1". These sure look like T12's, based on the size of ballast shown.