Fl-41 is the tint most commonly recommended by doctors and specialists for the prevention of light sensitivity and migraines. One study found that the use of Fl-41 glasses reduced the number of migraines by an average of 74% in a four month period. Fl-41 glasses are also effective at reducing photophobia and light sensitivity that does not result in migraines, particularly light sensitivity caused by florescent lighting and computer screens. SomniLight Rose FL-41 Glasses are rated UV 400, providing 100% protection against hazardous UVA and UVB rays. Effective for both indoor and outdoor lighting. Fit-over glasses measure: 160 mm (width), 160 mm (Length) 46 mm (height). Our Fit-over style fits comfortably over most prescription frames. We offer free US shipping and 60-day, no-hassle returns.