Hey Glockers! I just picked up one of these out of curiosity. It is a very sturdy design and locks up tight when installed. It came with an U-tool, extra power spring, and the extension (which is in 2 pieces). I love that it makes my 15 round mag into a 21 round mag and fits very flush with the end of the grip. Anyone have any experience with these? How have they held up for you? Obligatory Pic: Wanna kill these ads? We can help!