The G-3 inserts a shorter than the Freak inserts, about
2 1/2 inches long. And they screw into the base.
I've shot my friend's G-1 (shorter inserts) and it's great. I'm probably going to buy a G-3.
The only complaint I've heard about them is that they tend to unscrew. The inserts are counter-threaded, so screwing the barrel into the marker can cause the breach to unscrew if you're not careful. I've been told that using good washers will eliminate this issue.