NoIR filters can help people minimize eye discomfort and maximize visual resolution. Filter shade number 81 ‚Plum ‚allows in 20% of visible light, has 100% ultraviolet protection and is a general purpose filter with glare reduction for enhanced visual acuity. This filter also has Blue Blocker Protection. The standard fit-over style frame may be worn over most prescription frames or worn alone. It features side shields with temple lapped construction to keep out extraneous light and wind and it has curved temple pieces for a non-slip fit. Frame measures 5 1/2″ temple to temple.