HD GLASS High Density Sharp Cut UV Glass Chemically Enhanced Optical Glass is 4x Stronger HD COATING 16-layer (both sides) Anti-Reflective Multi-Coating Water & Oil Repellent, Scratch & Stain Resistant HD FRAME Wide-Angle Lens Compatible Ultra Thin Frame Glass Mounted with High Pressure Press Technology A MULTI-PURPOSE FINE-WEATHER FILTER Absorbs the ultraviolet rays which often makes outdoor photographs hazy and indistinct. A multi-purpose, fine-weather filter for color as well as black and white films. Also serves as a permanent lens protector.