Stapler attachment. Fits Pen and Gear brand from Walmart staplers (checking on other ones). To measure what size your turner arm is measure from outside edge to outside edge. If it measures about ¾ of an inch you need the ½ inch adapter. If it measures a little over an inch, then you need a 3/4-inch adapter. The Deno's turner arm options are for specific turner arms made my Deno's.