These Rock stepping stones are using FR boards. We have hooked them to an octo board. 
Comes in a pack of 4, 8 or 16 - Hooked to an octo board ready for you to hook your output on; light, chain or unchained to a maginet, sound, etc
 
Size Varied 8-10" wide  x 6- 8" long
Rocks are painted silver grey on 1/4 bultic birch as seen (no colors, just ready for you to clue as you wish)
Custom or simular demensions- description needed and will call you to verify (could be cut out for feet, hands, shapes etc)
 
Been using in escape rooms for 2 plus years and has work fanastic for traffic durability. 
 
See video click here