I am not 100% sure why exactly this razor produces very close shaves. I have used both Merkur 38C and Merkur 39C Slant, and 12C beats them down no questions asked. Although the blade gap on 12C is very shallow, my theory is that the open-comb design allows the blade come in a very close contact with the skin. In other words, there is no guard between the skin and the open-comb teeth: The blade is open. It is really aggressive and you must have a stady hand and solid technique before using 12C, however, you will be well-rewarded with a BBS every time. If this is not yet aggressive for you, the next step is a straight razor.