I bought some HF blades on Thursday I think I have been using them since and so far they have not hurt my mat (I used and old mat just in case) They seem to be holding up well Our store here is new and not many people shop there yet so they had a lot of blades in stock. I have tried them in all three of my cutters the Olfa, Fiskars, and the Martelli they seem to fit in all three