The Costa Del Mar Ballast Polarized Sunglasses is a member of their super-light frame-less collection that weighs in at a feathery 16 grams. And with TR90 nylon Ballast is as durable as it is comfortable. The nylon frame is rimless and has an internal hinge. The lenses are polarized with Costa's 580 technology that kills reflected glare and reduces eye strain. The Grey lens is for everyday natural contrast and the Copper lens is for driving and variable light.