They're called PERMA-SHARP double edge razor blades. The operative word here is - SHARP. I was using and still have Crystal Personna razor blades. Crystals are a good blade, but they simply can't compete with PERMA-SHARP when it comes down to which of the two blades has the sharpest edge. What this means to my morning shave is that I make fewer passes to cut the same stubble. I finish shaving quicker and receive a much closer shave, especially around my neck and throat. The mild razor burn I received from the Crystals has been eliminated. I should also mention that I shave every other day and I use a Merkur Progress razor set on 5. I ordered some Feather razor blades, but they never came - now I don't need them. If you want a close shave with fewer passes, little to no razor burn, then give these blades a try (good for two shaves maybe three). I'm confident you'll agree with my assessment of their very sharp edge. Cheers!!!