Currently, there are nine generations of Glock magazines.
If the Glock has the standard magazine release, then it can use all (1st-9th) generations of Glock magazines [Type 1-4].
If the Glock has the ambi-magazine release, then it can only use the newer (8th-9th) generations of Glock magazines [Type 3-4].
If the Glock has the reversable magazine release set up on the standard (left) side, then it can use all (1st-9th) generations of Glock magazines [Type 1-4].
If the Glock has the reversable magazine release set up on the non-standard (right) side, then it can only use the newest (9th) generation of Glock magazines [Type 4].
Even though there are technically nine generation of Glock magazines, they are typically simplified down to four types.
Type 1 = NFML (Non Full Metal Lined)
Type 2 = FML (Full Metal Lined)
Type 3 = FML with ambi-magazine cut
Type 4 = FML with ambi-magazine cut & reversable magazine cut
1st-8th generation Glock magazines. Type 1 = 1st-3rd gen. Type 2 = 4th-7th gen. Type 3 = 8th gen.
8th (right) and 9th (left) generation Glock magazines. Type 3 = 8th gen. Type 4 = 9th gen.