All of GLAS glasses have a CR39 lens, which is one of the best on the market and is characterised by its thin, durable construction and high optical performance. THE LENSES 100% UVA and UVB PROTECTION ANTI-FATIQUE ANTI-SCRATCH ANTI-DIRT ANTI-FOG ANTI-REFLECTIVE LIGHTWEIGHT Width 144 mm Height 59 mm Lens Width 52 mm Lens Height 49 mm Bridge Width 22 mm Temple Length 145 mm **Is this frame the right size for me?** Try on any pair of glasses or sunglasses that already fit you well to see if this frame will suit you. 1. Measure the actual lens width and bridge width on your glasses using a ruler. The lens width should be around 40-60 mm and the bridge width should be around 12-24 mm. 2. Multiply the lens width by 2, and add this number and the bridge width together. This should give you a number between 100-140 mm. 3. For the best fit, we suggest choosing a frame that is within 5 mm of this number. Enter your number between 100-140 mm below to more accurat