This is the one I have. I love it dearly! It's a steel turian style collar from house of collars. It locks with an allen wrench so it can't come off unless I am instructed to do so. I love when people know what it is. It makes me feel naughty. But, on the other end of the spectrum, I'm glad it's not more obvious since I am a full time student and retail manager. The only thing irritating about it is that it's quite uncomfortable to sleep in. I have to sleep in it for punishment sometimes. I wouldn't mind a leather collar to wear in bed.
Oh, it has an attachable d and o ring when we need it

http://www.houseofcollars.com/viart/...=0&item_id=147