Complex sentence: CR-39 is transparent in visible spectrum and almost is completely opaque in the ultraviolet range, it has high abrasion resistance, in fact the highest abrasion/scratch resistance of any uncoated optical plastic.
Split into simpler sentences: CR-39 is transparent in visible spectrum and almost is completely opaque in the ultraviolet range. It has high abrasion resistance, in fact the highest abrasion/scratch resistance of any uncoated optical plastic.