The price listed is for six acrylic stones. These are approximately 23mm opaque dark purple acrylic stones. These appear to be unfinished parts of a button. These have a smooth back with a rectangular 5.7mm by 3.5mm hole.
There is a 15mm square recess that can fit stones that may or may not have a shank back to make them into a complete button. These can also be used as beads, or spacers between beads.