D Clip Flip Up - "smaller frame styles" Our "patented, all metal" flip up mechanism securely clips to the top of your plastic or metal frame, allowing you to obtain polarized, 100% UV protection with our superior polarizing lens system, protecting your eyes from the sun's damaging rays and blinding glare. In addition, our polarized lenses are also highly scratch resistant. You now have the convenience of just flipping them up or down while boating, fishing, or just driving your car. Our patented flip up "all metal" mechanisms are virtually unbreakable, and the metal mechanism from our proprietary "sticky" vinyl clip coating system protects your lenses by preventing slippage and scratching. Here is how to measure your clip on sunglasses to ensure they fit your eye glass frames correctly: Carefully read through the clip-on sunglasses fitting tips below as it takes time and patience to get the right clip-on for your glasses. You must measure your glasses very carefully to get a good fitting clip-on, every millimeter in width or height can make a big difference. It's best to use a millimeter ruler but if you use a centimeter ruler, you can get the total millimeters by multiplying centimeter results times 10. (Example 5. 1cm x 10 = 51mm) 1. Measure the width and height of one lens including the rim. 2. Look at our clip-ons offered on our listing and choose the one with the closest shape and size. Always go to the next bigger size when in-between sizes. 3. If the rim is thicker than 3 millimeters, the clip-on will not attach to the frame properly.