Double Stack 9mm Pmag +2 Magazine Extender For Glock. These are 3D printed magazine extenders that will add 2 rounds to your pmag. They come with a sliding plastic locking piece that keeps the baseplate from sliding back. I recommend keeping the sliding piece as flat as possible with the baseplate when installing. I used pliers to pinch it into place. This also uses the baseplate that comes with your pmag, just slide it onto the bottom of the extender, this doesn’t require a new spring to work.