The glasses served its purpose. I use them in a UV-radiation. It takes about 5 minutes, if necessary, to establish the correct viewing distance by trial and firm back and Herverschieben the rubber band over the shells, since the rubber relative clamps on the shells and one first always attracts too far in the direction you want. But then the glasses are firmly "set" and is perfectly located; So a one-time expense. Sharp edges, I can not determine.