It is a quite sturdy silver ring where you can change the ball. Here I have a ball that matches my garden party nails. The man in the shop and DH really loved this combination.
It is a woman on the Isle of Nyord (a lovely little preserved island near Ulfshale at the Isle of Moen) who makes the glass balls herself. Both the ring and a lot of balls can be bought from her webshop: Runas.dk. The ring costs about 50 dollars including one ball of your own choice. I got one ball for free when buying six balls. A few days later I figured I missed two more colours so me and my SIL went to Nyord, because she was curious too. Now I can look forward to four more balls for my ring for my birthday. :)