We offer several different screw mandrels. To pick the right one for your application, you need to match the arbor hole of the item (felt wheel, brush, abrasive etc.) you are going to use to the arbor hole information provided. Keep in mind the maximum thickness of that item can only be 1/4" Also look to see if you need to select a mandrel with a reinforced shank. Our 840-3160 is made of stainless steel, the others are tool steel. Finally, please be sure to select the right size shank for your handpiece. All threads are right-hand.