The key with a hard material thumb ring of any type is fit. The fit is vitally important and the fact that your thumb changes size means that you really need to rings. I would suggest if you are going to buy one then to get one that is a size too small then enlarge the hole to fit. Adam Swodoba (spelling?) has written an excellent book on thumb ring shooting. For anybody new to shooting with the thumb ring this book is more useful than anything else! There are too many differences in the techniques of finger drawing /thumb drawing to think that you can do both and switch back and forth between the two methods especially if you have shot three fingers for a long time before trying to learn thumb ring shooting. It took me a whole year to really get the hang of it, shooting most days and I think I made about 12 rings to get that perfect shape.