Okay, they will increase about 10 fps if you’re going from a 6.08 to a 6.04/6.03. They are tighter barrels, so when a BB goes through your barrel it will have more air propelling it. The point of one is to increase accuracy, and range. By accuracy I mean the BBs will be more concentrated. I would recommend a Prometheus, because their barrels are of higher quality and are 6.03, but 6.04 and 6.03 perform pretty much the same. You just pay more if the barrel is built of stronger material. Some people experience feeding problem with the Prometheus, although I've never had this problem, and I have never cleaned or touched my barrel. I also would recommend you have someone good install it.
