Sundown Eyewear offers this convenient and lightweight clip-on 3-pack of blue light blocking lenses so you can change your lens based on the time of day and your activity. The orange block 98.5%, the yellow block 78% and the clear block 50% of all blue light penetrating your eyes from screens and artificial room lighting. These lenses are perfect for office and home use. Comfortable and easy wear while on the computer or tablet, gaming, using your phone or just living under artificial lighting. For best use, wear progressively darker lenses as the day goes on. Ideally, wear the clear from 1pm to 4pm, yellow from 4pm to 7pm and the orange from 7pm until bed. This will block increasingly more blue light as your get closer to bedtime. Blue light prevents the production and secretion of melatonin, a hormone required for good quality and restful sleep. Wearing the clear lenses all day is great too, to prevent eye strain and headaches. The clip attaches the lenses to most glasses. Coverage will vary based on your glass shape and size.