This is the 15 round Glock factory 9mm Gen 4 magazine for the Glock 19 compact pistol.
The factory flush fit mag for the Glock 19 compact, will not fit full frame Glock models.
The Gen 4 type is backwards compatible with all previous generation Glock pistols, as well as the newer Gen 5 (with the magazine catch installed in the default position).
Manufactured from hardened steel incased in Glock's trademark tough polymer these are very durable.