Stacking rings are supposed to be quite thin. You need to be able to wear between 5 and 15 rings at the very same time, depending on your finger length. In order to maintain them together and prevent uncomfortable movements, you will most likely have a clamp. Their clamps are generally fitted with a gemstone. In some cases, they are easy and can be set on the interior of the finger, so it doesn't look unaesthetic. A clamp doesn't just hold the stacking rings together, but also ensures they do not get over other rings you could wear on the same finger and trigger a messy look.