This is an incredible 9-in STEEL Sanding Disc. This disc was made by Nathan Caruthers (Nathan the machinist) quite a few years ago. Guys were tired of the aluminum discs getting dinged up. He finally stepped up and created these incredible discs. Unfortunately I never got to use it. And I have since sold everything I own. If anyone's looking for the absolute best 9-in disc for their sander this is it. I believe this has maybe a half a degree machined into it. Looking to get $150 shipped. PM IF INTERESTED. THANKS