I have the round kind that you twist and turn. I use it only in an emegency. It is only a band-aid, and I hate a cutter that chews its way across the fabric. I think you deserve a new blade when they get dull; of course mine will have knicks in it and that is really annoying and not fixable. I heard a lady at our Guild say she put a new blade in every time she cuts a new quilt. I would like that but my pocket book would be crying.