Modern lens material is very soft and during the edging process there might be a little swarf remaining where the bevel meets the surfaces. You want to remove this excess material and not run the risk of scratching the lens.
The curved edges on this blade help keep it balanced on the edge of the lens. We built in fine, squared tips for cleaning out the groove of a nylon cord rimless.
Made in the USA of spring steel mounted into a carbon steel nickel plated handle.