It is the gen4 iteration and comes with (3) magazines and the four back straps that typically come with Gen4 models.
Each GLOCK magazine is constructed from a hardened steel insert encased in high tech polymer to protect the magazine and prevent deformation, even when dropped from a great height.
Elite Tactical Systems Group, Elite Tactical Systems Group, Magazine, 10MM, 20 Rounds, Fits Glock 20/29/40, All Generations, Polymer, Clear
GLOCK, OEM Magazine, 10MM, 10 Rounds, For GLOCK 20, Cardboard Style Packaging, polymer, Black
Pearce Grip, Grip Extension, Fits Glock 29/20/21/40/41 High Capacity Magazines, Black
ETS magazines are made from advanced polymers that provide extreme impact resistance, so they won't crack or break when dropped.
Glock, OEM Recoil Spring Assembly, G20 & 21