Our Universal Nut has been re-engineered with a recessed back. Now you can securely tighten ALL King Arthur's Tools accessories to your angle grinder with this truly "Universal Fit" nut. UNIVERSAL NUT recessed back allows disc to be tightened on different size angle grinders. Choose either a 5/8" or 14mm center Universal Nut. NOTE: Only blades with 5/8" (16mm) and 14mm center hole sizes may be tandem mounted.