Tumblestones have both advantages and disadvantages and users will have their own opinions on the subject, but here is my own opinion.
Most Tumblestones are in three sizes, small, medium and large, but you can get extra large from some suppliers. Generally small ones 10 to 20mm medium 20 to 30mm large 30 to 40mm extra large 40 to 50mm but check with your supplier first as people rate them differently.
In crystal healing where they can be placed on the body, I find them a nightmare as with the slightest movement, they will roll off you or your patient. For the purpose of healing where it's best to place crystals on the body, I use Natural Healing Crystals as they have unusual shapes where you can find a surface that will rest easily on the body and not roll off.
Again in crystal healing I prefer the Natural Healing Crystals or as some call them rough rock as it is believed that they hold much more energy than a Tumblestone because they have not been cut into then tumbled and finally polished, all by machines, which makes perfect sense to me.
Saying all that doesn't mean that Tumblestones don't have a place or purpose in the world of crystal healing. They still hold lots of energy and one big advantage is they can be placed in your pocket knowing full well there are no sharp or rough edges that could hurt you physically. This means they can be with you through the day giving your body chance to absorb the Tumblestones energy. If you are looking for protection from negative energies around you, for instance, at work the then having the right stone in your pocket has a great advantage.
Go shopping now and absorb some of natures natural healing energies