This is a tension ring based on a clay model I made before. It is very easy to use, just like using your finger but with a cover. I prefer this way that other types of tension rings as it feels more natural. Besides, you can choose to have a cat or a frog as your knitting/crochet buddy. The buddies help the yarn stay inside the ring, for best results use it as in the pictures. Finaly to make them more interesting I painted them.

I recommend sizing it to your liking:

1. Get the diameter of your finger. The model has a diameter around 1.65 cm. 
2. In the toolbar choose the resize tool and add or take the mm you need.