Have been in cb series for last 7 years with a 2 week stint in birdlocked. Just got new CB6000s and after 24 straight hours, have discovered that it is very secure, conceable and comfortable. Even forgot a few times today that I even had it on. Read a lot of reviews on the 6000s and was hesitant at first, but so far am very pleased. Started out with largest ring and smallest spacer and seems to be a good fit, at least for now.
I used the 6000s for about a year and for the most part it was good. After a year though the seam split just above the locking pin. Some super glue and sand paper and we were good to go again. Shortly after that i noticed a slight pinching sensation of my scrotum just below the tip of the tube. After inspecting it I noticed that the seam was beginning to separate at the top and bottom of the tube. More super glue and sandpaper. However this time I had to sand inside the tube and was never able to get it as smooth as it was and never was as comfortable as in the past. Recently replaced it with a Jailbird.
The thing about off-the-shelf items is that they are one size fits all. Unfortunately most people aren't that one size. Occasionally though someone will be that "one size" and it will all work out just fine. You are lucky The seam split appeared to be an issue a year or so back, and if the CBXXXX was an original Millers device they were happy to replace it. A lot of people have managed to glue and sand their device as stated above and still get plenty of wear out of it.