This is going to be an arm cuff. I have crocheted this using a hook that came in one off those high light your hair kits (Gems hair a while back now) that you pull the hair through the cap.
Worked just the same, but I guess the end is a little sharper as it has to hook through plastic.
I am going to attach both edge with ribbon like a shoe laced up, to make an arm cuff they seem very in with the teenagers.