This is the standard ball latch used in almost every Tippmann paintball marker.  You know you need one of these when your marker is double loading paintballs, paintballs are rolling down the barrel, or your are getting paintball breaks in the breach area.  You can look at your existing ball latch by removing the barrel (making sure you do not have compressed gas attached to the marker).  You will see the small orange piece in the bottom of the breach.  If it is not curving up into the breach (or missing entirely), you need a new ball latch.