The best single edge razors.
After trying many razors, all Derby razors are the best for sharpness and longevity.  While maybe not the absolute sharpest, they last much longer than most because of their coating.  I don't like razors that are so sharp they cut, nick, and weep, so it does depend on preference.  If you want a good smooth shave and a razor you can get more than a few shaves out of, I would highly recommend these.
Rating: 5 stars