Stocklense Finished Bifocal CR 39 FT-28 First Quality Stock Finished Lenses Material: CR 39 Size: 70mm Lens design: Spherical Coating: Uncoated, Fast Tint Refractive index: 1.498 Specific gravity: 1.32 ABBE value: 58 Availability Chart: Technical Data of CR-39 Uncoated: