I was frustrated with the "carpet cutting" blades from Harbor Freight that I was told I could use in my Olfa rotary cutter. Yikes... that didn't work at all! I was so excited to be saving that much money, but man they didn't cut a thing and where not "smooth" rotating. So... still buying the crazy expensive ones for now. I did order some cheap ones through a co-op...but as cheap as they were I'm worried they're like the Harbor Freight ones. We'll see!