Basically: 1. Take this barrel replacement and replace your barrel with it: 2: Press it up against this to fill it with CO2, in the same way you refill lighters with butane: Then shoot it. The CO2 causes the pistol to cycle, and a laser is fired so you know where your simulated shot went. It comes with a simple target, but it works with all the laser target systems out there. One reload of CO2 is good for 15-25 shots, or you can get one of these for something like $200 which stops you from holstering, but increases the CO2 capacity immensely: This is the entry-level system called the Cool Fire, which costs $400 and includes the laser. The top end is the TRS and it includes an IR laser, no protrusions from the gun, CO2 stored in the magwell area instead of the barrel, upgraded components, and so on to justify its $2,400 price. There's another model in between these two as well. To me, this seems like a simple, cheap system that will let you practice indoors with your carry weapon. More people should know about it.