For the oval shape to fit your glasses, your glasses need to be similar in shape with your frame rim measuring less than 3mm's thick. Please measure one lens of your glasses carefully to the outside rim of your frame width x height. The clip on is designed with a spring in the nose bridge for tension to keep the clip on your glasses securely. The oval square shape needs to be nearly the same shape as your glasses and the size clip-on sunglass needs to be the same as the measurement of your frame or the next size bigger. Sizes Available 48mm Wide x 36mm Height polarized 50mm Wide x 38mm Height polarized 52mm Wide x 40mm Height polarized Say goodbye to the hassle of switching between glasses and sunglasses – with our sunglass clips for men and women, you get the best of both worlds in an instant. These durable clip-on sun glasses are lightweight yet robust, offering long-lasting wearability through all seasons. All of our sunglasses and clip-ons are rated UV400 protection which is up to 100 Percent protection. Included microfiber carrying pouch.