I've been through a few chest protectors lately. Vaughn, Brown, Bauer. I felt like the three little bears. This one wasn't protective enough, this one was too bulky etc. Then I went into Total Hockey near me for a sharpening and I just decided to try on the 11K for fun while I was waiting with no intention of buying. I was wearing the Bauer Pro, and the fit was just a bit too small on me, and found the protection in the arms a bit lacking for a pro-level c/a, but it wasn't so bad I felt I needed to replace it.
As soon as I put the RBK on it was basically love at first sight. I've never been a RBK fan of Reebok chest protectors in the past. I've found the c/a's to be too bulky and restrictive. This however seemed to be a perfect mix of protection and bulk.
After wearing it for about 2 months now I've just become more and more impressed with it. It fits like a dream, and protection is top shelf.
I'll admit the sizes are really strange so I would not suggest buying it sight unseen. The jump between small and medium was night and day. Usually I'm borderline small/medium usually opting for the small for mobility purposes. There was no doubt on this one. I'd say RBK's medium is closer to other companies larges. Also it's heavier than the Vaughn and Bauer pro models, but with that weight comes better protection so it is a tradeoff. Though you shouldn't be ruling any product out because of ounces.
Overall this is the happiest I've ever been in a c/a for a long time.