Hey there.If you look at the photos.. there are caliber-specific valves. So .177 / .22 are the same, then .25, .30, .35, and then .45 and .50 are the same. Additionally, you'll need different hammers and hammer springs. Each caliber kit will come complete with whatever you need to run that caliber. It's not an "instant" swap out, but it's not that hard to do either. I've got a busy week, but I look forward to getting more data out on this soon. CheersRick