I replaced my blade yesterday with one of them and man was it sharp. The ladies at my little sewing group gave me the money to go and buy a bunch for them on Tuesday next week when I get back over there.
One lady had a cutter, I didn't pay attention to the name of it, but the original blade hole had like a 3 sided circle, I don't know how to describe it it looked a bit like 3 flower petals. Anyways the blade worked on it too. So that doesn't matter.