This is something I was researching when I was planning on getting guages for my car...i'm pretty sure the smaller guages are 2 1/16", if you want the flush mount, my old car had a 2 5/8" guage for the oil guage and it did not fit flush, but the ring stuck out.
Thanks mate, I thought they were 2-1/6" but wanted to double check.
OK, now I'm a little confused, which one of the photos below is what you'd call flush?
As you can see, they're all different. The 1st photo is basically stock, way down, (looks hard to read). The second photo (the one you posted) is what I'd call flush, so you say 2-1/6" for that look? The third photo stick out so I'm guessing these are 2-5/8", correct? Sorry for making a mountain out of a mole hill, just want to be sure.