Pretty good. Sadly, when the gun arrived they had popped off. If it becomes a problem, there's no reason I couldn't fit top hats. Also, because of the surface area of the ram, the air pressure used is really, really low.
Edit: I just aired it up. It sounds, and feels right. It cycles nicely. I gotta hand it to the guys at Powerball, they can time a gun. ... and have it survive the trip across the pond... and still have it timed.