I have seen them on YouTube and Instagram, but never in person until today. There were three different lowers. One for an AR-15, AR-10 and Glock. http://www.polymer80.com/pistol-frames/ "This product is compatible with Gen 3, 3-pin: 9mm Glock 17, 34, 17L. .40S&W Glock 22, 35, 24. 357SIG use .40S&W Slide Glock 31, 35, 24." The handgun looked pretty straightforward since the template over it showed what size holes to drill and an area to mill out with a dremel. One gentleman told me a limitation of the handgun is that it doesn't lock back on the last round. Any experience with these handguns? It would be a fun project but I'd guess the cost would be close to that of a Blue Label Glock, or more if one used Zev or other third party internals/components. The AR receivers looked like a lot more work to do as they require a drill press. They sold the drill parts, the jig and lower. How exactly easy or hard is this to do? Lastly, They said the firearms couldn't be sold. How exactly would that be tracked or enforced? How exactly would a gun like this be processed if it were involved in a self defense scenario? It would take some degree of effort and maybe skill, but I don't know. Any firsthand experience with these? It's very intriguing, at least.