The Silver Bullet 2 (SB-2 for short) was the successor model to the original Silver Bullet. Released by Tom Kuhn in 1990, the yo-yo featured the first modern ball bearing axle and a patented string gap adjustment mechanism. By unscrewing the yo-yo halves and adjusting the depth of the bearing cups which screw into the halves, the user can set the width of the yo-yo gap to accommodate their personal style of play, by means of a screwdriver-type tool. Also released was a Butterfly-shaped variant, the Tom Cat.