I've been kept in the CB6000 for as long as 5 months; it comes with 5 different size rings and given the chance to work a good snug fit, is reamisterably comfortable (considering the maddening urge to rip it off and get myself off). My KH likes it, too, cause she can see just how aroused I am when I'm poking out the end of the thing in the morning.

I don't have the metric conversions, but I'm 4.5" in girth and 7" long erect (yeah, a true pencildick). The 6000's really snug, and it's impossible for me to pull out of (with the right ring); it's a good 'fit' for us. I'm going on my third week 24/7 without so much as a touch.