US Darts Dart Shark - Multi-Purpose Dart Tool, Dart Mechanic + Round Dart Sharpener + 25 O Rings + O Ring Applicator Multi-purpose dart tool. For both steel and soft tip darts Tightens tips and shafts, Split the end of shafts for east flight insertion Round stone - Removes burrs from dart points and extends the life of your dart board. A sharp point penetrates the board reducing the number of bounce-outs. Applicator is a handy tool for applying O-rings to dart shafts. Keep your metal shafts and barrels locked.