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Kai blades are not as sharp as Feathers, but they are longer lasting. They are a thicker blade, and not as flexible. This is noticeable in the Blackbird and in some slant razors. They do not have any soft sticky wax on them, to gum up your razor. I like Kai blades, but I like Feathers better.
More than reasonably sharp, but not as sharp as Feather.
Long lasting. A thicker blade than Feather or Astra.
More expensive than Feather, and harder to come by outside of Japan. There are other equally good blades available at lower prices.
Very good quality.
Very good packaging. No sticky wax on the blades, like Feather and Astra have.
I tried the Kai as all reviews were glowing. It's said the blade is thicker and if that is true a guy would need a micrometer to show it. I found it very similar in flex to the Feather. It is said to be wider than the norm but again, I found it to be pretty standard when compared to feather, Voskhod, Personna, and Polsilver. I have grey whiskers and it seems to be the opinion of many that grey is harder to cut than colored whiskers. I don't know if that is true but I do know that I seem to favor the sharper blades. Feather, PolSilver, Nacet, Permasharp are some favorites. In my experience, the Kai doesn't hang with that crowd. Hey, it's a razor blade sure enough so it's very sharp but on my chin I found it to perform similarly to the Dorco; not tuggy but not efficient either. My shaves have been comfortable but far from easy. It takes me 4 passes with a massive clean-up to get where a Feather takes me in two passes. I tried it in a Rockwell (4 and 5), Jagger DE89, Mamba, Gillette Fat Boy (4, 5, 6). I sure don't hate the blade like I do the Merkur but I'm sure underwhelmed. Giventhe price, and the lack of performance, I see exactly zero reasons to ever have Kai in my kit again.
middle range sharpness
Seems to last similar to others. I get three shaves before noticeable drop in performance.
Seem to be made of quality steel
They don't have wax dots but many of my favorites do