1- It opens completely to allow you to regulate compression according to needs and ensure active support that adapts your body to your needs. 3- The breathable and ultra slim material on the back of the knee ensures excellent comfort and extreme lightness To identify your size you must measure the circumference of the 16cm thigh above the center of the patella. If the result is between the 2 sizes, choose the largest. 1- IT Opens Fully to Allaw for Ideal Compression Adjustment to Ensure Active Support That Adaptts to Your Body and Your Needs. 3- Ultra Slim, Breathable Material at the back of the Knee Ensures Excellent Concert and Extreme Lightness To Find the correct size, please mesure the circumference of your tigh 16 cm above the center of kneecap. If Your Measure Falls Beteween 2 Size.