An interlocking collar (72) secures a bag neck (46) in a keg aperture (42) of an alcohol beverage keg container (22). The interlocking collar is mounted in press fit surrounding relation with a peripheral wall portion of the bag neck. The collar has an outer peripheral wall portion sized larger than that of a keg aperture. The collar (72) has a recessed groove (76) in the collar outer peripheral wall portion for receiving in press fitting and sealing relation a keg flange (40) that defines the keg aperture. The collar outer peripheral wall portion has a resilient edge portion (78) adjacent the recessed groove that deflects to permit the interlocking collar to pass through the keg aperture and receive the keg flange in the recessed groove. The interlocking collar has a plurality of locking passageways (80) placed around the interlocking collar and axially extending through the interlocking collar between the neck and recessed groove. A latch member (82) has a plurality of locking fingers (84) that extend axially through the locking passageways to prevent deflection of the resilient edge portion of the interlocking collar after the collar is placed in the keg aperture.