I am a straight razor user (as my screen name implies), but I do occasionally use my mach 3 when I am in need of a very quick shave. I have recently come across some of the chinese knock-off mach 3 cartridges and I am wondering how good they are or aren't. They are incredibly low cost in conparison, so I am curious. Has anyone one tried them? How does the quality compare to those readily found in department stores?