No swabs allowed.
Sizers are tiny.
Not amazingly efficient.
The main downside to this barrel is that the sizers are 1'' long. When you are using a cocker, this makes it so that you have to put a little allen wrench into one of the holes and un-jam the sizer every time you have to change them. It also might affect efficiency a little bit. You also can't use swabs with this barrel because they can cause the carbon fiber to unravel. I don't find this to be much of a weakness though because straight-shots and pull-throughs are much more effective squeegees anyway.
Other than that, this is one of the nicest kits I've used. Out of all the barrels I've seen, this one comes in second next to the Scepter. On my Series five, I was able to shoot a 9'' pattern at about 50-60 feet using ZAP Tork. Considering that it's cheap paint, that was some really good accuracy. With Marbs it will probably improve.
I don't mind heavy equipment too much, but the lighter my setup is, the better.
Some people claim that this barrel can shoot through breaks [there are always people who say "(insert barrel name here) is the best" but they are rarely correct]. I don't believe that a truly self-cleaning barrel will be produced any time in the near future, if ever, but this barrel does recover fairly well from breaks. You should still use a straight shot, but you aren't completely screwed if a ball breaks in one of these. I have an SP All-American and Progressive, both of which shoot fairly well, but they will NOT recover from a break.
Overall this is a great kit.
It's pretty expensive, but you get what you pay for. Comes in a nice case too.
I beg to differ on the self cleaning portion. Both this barrel kit, and a J&J ceramic barrel I have claim to be "self cleaning." Now, it's not going to be spotless on the inside if you do break, if you do break a ball, after 3 or 4 quick shots, I am able to recover about 90 percent of my accuracy. I'll still run my straight shot through it later on when I get a chance, but I'd say that qualifies as self-cleaning, seeing that I don't have to clean it during the heat of the fight and it regains it's accuracy by itself.