This allows the CA$H 9k and RAD 9 and 45 to be mounted to a pistol with a tilting or reciprocating barrel. The Booster Assembly simply mounts to the back of your pistol suppressor and then can be threaded directly to your pistol barrel. – The RAD 9 and 45 ship with a booster assembly. – **The CA$H 9k ships with a direct thread adapter and will require the Booster Assembly to be used with pistols with reciprocating barrels.