The design of these coasters has undergone quite an evolution to get to where it is now.  Each has 16 caps crimped back to back in a ring.  They are set in an MDF base which is filled with a two part epoxy.  Our inventory is typically stocked with 200-300. IF we don't have what you're looking for, custom designs are no problem. They are $13 each or $11 each for four or more.  Contact us if interested.