These retractable reels have a vinyl coated woven steel wire so they last a lot longer than cheap retractable that normally have a string.
Comes in two styles. One with a belt clip. The other with a rotating latch hook.
Both have a spring clip on the wire end.
The Latch Hook style is a great way to hang your towel to your bag so you don't loose it but can pull it away from the bag for better use.
The belt clip is good for keys or office badges.