Our line of fit-over frames is specifically designed to be worn over your prescription glasses. They allow you to take advantage of the best Blue Light filtration technology for both indoor and outdoor use. Please note in order to serve as many customers as possible these are a universal fit (one size fits all) and are not adjustable. The frames are very light weight and the frame material is very flexible. We encourage you to download the fitting guide (found on the style page), print it out and place your existing prescription frame on top to approximate sizing.