This is the Sherwood Onyx ARL Anti-Reflective Lens Mask for Spearfishing and Freediving Features: Low profile, low volume mask Anti Reflective Lenses (ARL) Stealthy matte black finish Push button buckle With the Onyx ARL mask, we have taken one of our best selling masks in the Onyx and upgraded the lenses with an Anti Reflective coating. These Anti Reflective Lenses (ARL) start as Sherwood Crystal Clear lenses and are treated with the Anti Reflective coating. This process of coating the lenses reduces the amount of light that is reflected by the Crystal Clear lenses. This permits additional light to pass through the lenses to the diver&';s eyes. The additional light translates into improved contrast and optical clarity. Typical tempered lenses allow 92% of the light to pass through. Crystal Clear lenses allow 95% of the light to pass through. ARL lenses allow 98% of the light to pass through to the diver&';s eyes.