All Eyewear is measured according to these 5 variables. The 3 that are most essential are Lens Height, Bridge Width and Temple(Arm) Length.
All frame styles are built to these measurements and learning what measurements "fit" your facial structure or meet your visual preference is key to purchasing frames anywhere and especially online.
Please use a millimeter measuring device(i.e. rule, phone app) to determine your 3 essential variables as this will greatly simplify seeking and selecting the appropriate frame style.
With this information in hand, you can ensure that the frame style that catches your eye(every pun intended) will ultimately offer you the best fit.
Frame measurements can be found under the "SIZE" menu once a particular style is selected.