I have a pair of new wayfarers which I love, and decided I wanted some aviators. I chose gunmetal grey, g-15 XLT, nice understated color, and not mirror lenses. But beyond being absolutely sure which color I wanted, I ended up being the Goldilocks of sunglasses.

 First I got the small 52mm aviators, which ended up being WAY too small for me. I learned the hard way that the mm sizes is not specifically the distance across your face, it's the size of each lens. I have the 52mm in the new wayfarers which fit perfectly, so don't let that lead you to a size in aviators, because the size doesn't translate. So then I got the 55mm in the aviators and they were a tad snug on the side of my face. Then I ordered the 58mm. These seem to be the best choice for me and I realllly love them. They're lightweight and comfortable.

In the end, I learned the mm size will have a little to do with the distance across the face, being the lens get bigger, but it just wasn't as cut and dry as I thought. It's really best to try these on in person before ordering to know which size fits you best. Good luck!