Great for chastity use, my girlfriend can put one of these on and monitor me to make sure I'm not letting myself out while she's away on trips or at work. The numbers wear off after a little bit of time but it does take a while to be fully faded
Nice locks, that can pass through a metal detector.
Only down side, is they can be removed with a bit of a pull.
Handy and value for money.
These are a handy item to quickly get your sub locked up without worrying about a key. Great to keep on hand. The numbering system is a cute way of keeping track too.