To clear things up. The 8.1 magazine is the same as the First Strike magazines. The First Strike/8.1 magazines will work on the 8.1, the 9.0 and the 8.0 guns. There are rumors of a 9.1 in the works, but Tiberius Arms has not officially announced a 9.1 gun yet. The 8.1 guns CAN NOT use an 8.0 magazine.