The hexagonal nuts feel awesome to fiddle with. popular with the coin & key jinglers.
 
I love using it on my thumb or rolling it in my palm.
 
Roll up & down finger, toss & rotate in your palm or jiggle. A number of varieties available, both in size of ring & nuts. The small & medium are the same size bigger ring however with different size nuts.
 
It is a great stimulating sensory item, will lots of movable parts, ridges and smooth surfaces.