Shipping couldn't be faster. I bought them for competition and so far haven't used them there, but in my testing they work great with no modification to the mag' required. Installation is a breeze and they are very well made. When I contacted ZR Tactical my inquiries were handled rapidly and the questions were answered fully. These mag' extensions were suggested to me by B&T USA. Also a pat on the back to B&T USA, great folks and fantastic customer service.