3 ms·
CR-39 is great. They're scratch resistant, light, have high Abbe number (basically a measurement of the rainbow effect; higher is better), and UV opaque. I've
by corey_moncure 9y ago
CR-39 is great. They're scratch resistant, light, have high Abbe number (basically a measurement of the rainbow effect; higher is better), and UV opaque. I've had a pair of CR-39s in a lightweight titanium frame for over 15 years and still going strong.