For my Apple arrow saw i use the 3" cutoff wheels from Harbor Freight. You can get a 10pk for $5. The saw itself is 8,000rpm and HF cutoff wheels are 22,000rpm max, so perfectly safe. Although it's 40grit they will still cut like butter. I've been using them for years with no problems. Do not get the 4" because it will likely hit the metal guard/cover on the backside. Just to be certain i measured on my apple saw and there is exactly 1/2". Sure you might be able to squeeze a 4" on there with no room to spare... But don't risk it because upon start up the saw is gonna vibrate and possibly bounce a bit before reaching it's rpm. Hope this helps.