XTech Tactical's H&K VP9 magazine extender adds 5 more rounds to your magazine. Price is $29.95, which is lower than competitors already on the market such as
Taylor Freelance($39.95) or
HKParts($39.95)
Link:
http://www.xtechtactical.com/mtx-vp9p30-5-magazine-extender-with-spring/
From: XTech Tactical