These are your go-to lenses for those sunny, bluebird days. With a highly reflective, scratch resistant coating on the outside, Sol-X lenses are some of the more premium lenses available. The red Sol-X lenses from Smith allow only 17% of visual light transmission (VLT) through the lens, while their green Sol-X allows only 15%. VLT is the amount of light from the visible spectrum that passes through a form of eye protection. Lenses with lower VLT percentages help protect your eyes from the suns harmful rays while giving you a clearer field of vision.