CB6000s? Sizing and Advice for First-Timers

I haven’t started my chastity journey yet, but I’ve dreamed about it for years. The issue is that I’ve decided to buy a CB, likely the 6000s model, but fitting details are hard to find online. Sure, they mention tube diameter and inside length, but here’s the catch: I DO have a small member (I was quite disappointed when I realized you must measure from the top down, not the bottom. My erect measurement is 6 inches, which dropped to reality as only 4.25 inches, and my soft size is just about 1½ inches. I assume the 6000s will fit correctly. Does anyone have advice? I am fairly certain that for now, I want this specific CB brand. It seems less intimidating for my wife, and I don’t want to trigger alarms at TSA checkpoints in airports.

I plan to order next week, so a quick reply would be very helpful. Thanks, NeedsLocked