Most people use 325 for lapping. You can use the x coarse but the 325 is great.I have never had issues with the 325 being too rough to lap with. Finer grit will be ruined IMO if you lap with it. I never did but that's what I have heard. I bought the Norton lapping stone and it needed to be lapped before I used it. I spent about 55 on the 325. Well worth it IMO.