Pro Mag drum magazine is compatible with your Glock 42. It is constructed of DuPont Zytel polymer with full length steel internal insert, injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA.
Specifications:

Caliber	380 Automatic Colt Pistol (ACP)
Capacity	10
Finish	Black
Model	Replacement Magazine
Material	Polymer
Type	Detachable
Model Fit	G42
Brand Fit	Glock
Max Capacity	10