I ordered the first pair of these a few months ago for my husband. I measured his glasses & determined that he would need the Large Size LensCovers.

For the most part he likes the polarized LensCovers, but finds them a little heavy which makes them press down on his prescription glasses.  After wearing them for several hours he usually takes them off for a few minutes.  It took him a while to get used to the wider, wrap around frame, but loves the fact that the frame blocks the sun from his eyes.  The side lens helps with peripheral vision, but also lets the sun in at certain times of the day.

We expected these sunglasses would look clunky, but surprisingly, they don't look too bad.

 I deducted one star because the bows  touch the lenses when they're closed  -  so be careful not to scratch the lenses when you close them.

My husband likes them so much that we will be purchasing a total of 3 pairs.

I copied the following from the product description:
>>>To choose the correct size LensCover, be sure to measure your prescription glasses.

 How to measure your prescription frames for LensCover sunglasses:
1- Measure the widest part of your prescription frames left to right, this is the "width". Next measure the height of the lens with frame included.
2- Choose the LensCover frame (below) that is slightly larger in width and height than your frame measurements.
----Small is 5-5/16 inches wide x 1-5/8 inches high
----Medium is 5-1/2 inches wide x 1-3/4 inches high
----Large is 5-3/4 inches wide x 2-1/8 inches high
For example, if your prescription frames measure 5-1/4 inches (width) x 1-1/4 inches (height), the correct LensCovers Frame would be size Small.<<<