Holy Trainer Version 2: I bought this one recently (2 months ago). I was actually shopping around for a metal device, and got an email from the HT manufacturer that they had a new improved Holy Trainer with integrated locking mechanism. After a couple of emails with the manufacturer (very fast and courteous responses) I decided to order it. Got it in a few days, tried it on and immediately felt the improvements.
The new locking mechanism is very well designed. First it holds the ring and tube solidly together and in place. There is virtually no "play" or ability to move the tube away from the ring, or side-to-side, in spite of the device being plastic. When locked in place it feels very much like one solid and secure device.
As others have said the comfort level is as good as can be expected for any ring/tube type device. A second big benefit is the elimination of the external padlock. It so much nicer without having that padlock clicking, poking and moving around all the time.
The internal lock also eliminates the mechanical "play" introduced by the padlock, resulting in better comfort and security. I had become so accustomed to the unpleasant aspects of the padlock that it is taking some time to get used to it not being there (a good thing every time I realize its not there).
Anyway, Holy Trainer Version 2 is the best device I have experienced to date. I'll post another update after I've done a longer chastity term in it (which should be soon).(Source)
Why not introduce some Female Centered Femdom to your relationship?