I have played with an earlier version, the strut-and-cut. It had a different(and much more annoying) lock mechanism, but was still an interesting knife. From what I could see of the interior, there is a tiny gas/spring cylendar attached with a pivot to the blade. Once the user has opened the blade partways, using ridges on the butt, the springy thing takes over. The opening was nice, but the blade wasn't too great 440a I think.