Medium Size Fit Over Sunglasses

Step 1.  Measure the widest part of your prescription glasses from the outside left temple to the outside right temple.
Step 2.  Measure the height from the top of your frame to the bottom of your frame.
Step 3.  Your prescription glasses must be smaller than the measurement of the fit over sunglasses styles listed below. 

Style F11: 5 1/2" Wide x 1 3/4" Height
Style F1:   5 5/8" Wide x 1 7/8" Height
Style F27: 5 5/8" Wide x 1 7/8" Height