This is by far the most comfortable and secure chastity device I've ever worn. Have worn it more or less continuously since receiving it, and at this point, it only comes off for routine maintenance, or for Master's use. Have experienced no significant discomfort, and already it feels like a part of my body, no different from a filling or a prosthetic limb.
I was pretty nervous about getting the measurements right, but the instructions are clear and easy to follow. No complaints, couldn't be happier.
A note on sizing: I have an 8ga PA, and that's been fine for me.