Designed by Hannes for high function, made of 5/8” dia rod for no-flex performance. This larger diameter is easy to hold on to in use for better control and chatter free sanding even with the 5” disc. Each is drilled and tapped 5/16”-18 to accept the soft edge pad and has a set screw so it can be operated in reverse. The other end is turned to 3/8” to fit in your drill chuck.