LIFE TIME WARRANTY -100% risk free to try, unsatisfied glasses can be refunded within 90 days of receiving. Customers will enjoy lifetime warranty(not man-made damage). In case of any problem happening, just contact us without any hesitation until you are satisfied. LENS TECHNICAL CHARACTERISTICS - 1.Multifunctional coatings,like UV400 protection, anti scratch coatings. 2.Reasonable blocking rate.Firmoo computer glasses lens' blocking rate are designed at about 40% considering two reasons:Higher rate would cause color distortion, lower rate would not protect your eye effectively. FRAME TECHNICAL CHARACTERISTICS - 1.Light weight TR90&Metal frame for less pressure on your nose. 2.Replaceable lens to meet your reading glasses or sunglasses needs. 3.High wear-resistance, hard to break and 90 days return policy is another quality warranty. 4.Skin friendly without causing allergic reactions. NO MORE TIRED EYES - We are directly exposing to blue ray from phones, TVs and computer screens over 8 hours every day,please don't worry,Firmoo computer Blue Light Blocking Glasses help you with discomfort like eye strain, migraine, blurred vision and hard to sleep. DESIGNE CONCEPT - When you spend much time on social media, Firmoo anti blue rays glasses help to reduce eye strain and headache by blocking blue light for you. Besides protecting your eyes, Firmoo oversized computer glasses are perfect accessories to show yourself on social media.Special designed oversized square looks would shine your style out from other people. Lens height: 49 millimeters. Plastic lens. Metal frame.