The Costa Del Mar Men's Harpoon Polarized Sunglasses are virtually indestructible with these nylon frames that offer the perfect blend of durability, comfort and style. The frame is made of heavy duty TR 90 nylon frames and has an optical spring hinge. For serious outdoor adventures, you need polarized sunglasses that will stand up to the elements. The lenses are polarized with Costa's 580 technology that kills reflected glare and reduces eye strain. The Blue Mirror lens is for harsh sun and has a natural contrast. The Green Mirror lens is for bright sun and has a high contrast.