Another 3D Printed kit from PJWRKS in this overview video of the 3D Printed Airsoft Modular Glock SBR kit that can be downloaded from Cults3D... "Hi! This is a Modular Glock. The grip is size 17, and the rail part can be replaced by 19/17. It is the M3x30mm bolt and the M3 nut that secure the magazine holder and the rear rail.