The Drumlok® security system replaces either your bolt ring, in the case of an open head drum, or your plugs, in the case of the closed head drum. They prevent unauthorized opening of drums by securing them with a keyed padlock. They fit on either a 30 or 55 gallon drum, and you can sleep safe know that it has secured the contents of your drums.
You will want to grab your padlock as well. Those are sold separately.