SIZE depends on THE UPPER ARM CIRCUMFERENCE (biceps) and the arm length. How to choose，can refer to the fourth picture. | MATERIAL--80% nylon (polyamide fibre) 10% spandex 10% SILK ICE fabric. MUCH BETTER THAN other material, FIT WELL, VERY SOFT and SILKY, NEVER FEEL TIGHT, thread not loose, anti-pilling | COOLING Unisex Arm Sleeves Protect up to 99 Percent of UV Caused by the Suns Harmful Rays. It helps to protect your skin and feel COOLER than bear skin. is quite SNUG, lightweight and bearable in the heat.COOL COOL COOL outdoor or indoor because of silk ice fabric. | THE FIRST CLASS QUALITY--- long lifetime, look decent, The stitching seems to be a decent quality | For All Outdoor Sports and Activities, such as golfing, cycling, fishing, driving, jogging,running,biking,motorcycle, claiming, boating, gardening, basketball,baseball,football,volleyball, tennis and so on. Great skin protection when you working outside or doing any outdoor activities. Suitable for Indoor Activities too, even your workplaces (Your arms won't sticky on your desk). In winter Arm Compression Cover Warmer