Glock magazine capatibility is dependent on the type of magazine release on the Glock.
Glocks with the standard magazine release can use all generations of Glock magazines.
Glocks with the ambi-magazine release can only use the newer generation of Glock magazines, the ones with the front side mag release cut.
Glocks with the reversable magazine release set up on the standard (left) side can use all generations of Glock magazines.
Glocks with the reversable magazine release set up on the non-standard (right) side can only use the newest generation of Glock magazines, the ones with the right side mag release cut.
There are currently eight generations of Glock magazines that have been simplified down to four generations.
1st generation = non-full metal lined
2nd generation = full metal lined
3rd generation = full metal lined with ambi-mag release cut
4th generation = full metal lined with ambi-mag release cut & reversable mag release cut