I couldn't find one of these at any of the "big box stores" so I got it from here, which is better anyway since I probably would have paid more at the store I'm sure. These wheels don't wear down for a long time. I've still got the original in my 500X and that's after sharpening at least 100 bits many times over. In my opinion the grinding wheel is better than the machine itself, at least the 500X (see my review for that if you wish).