Alpine951

I was actually trying to check the side clearance of the rings but this question will also apply when I check the end gaps. The factory manual says the side clearance for groove 1 = 0.04 - 0.072. Is this millimeters? I have some feeler gauges but it seems like the ones I have are not thin enough. The thinnest one is 0.102mm. I walked into an autozone to see if there where thinner gauges than the ones I had and they had the same exact one I had. Are there thinner ones? Also is groove 1 the groove closest to the top of the piston? The package for the Goetze rings I have show groove 3 at the top of the piston.

Alpine951

Google search reveals yes, there are thinner ones. Just not available at local Autozone.