These are dog training buttons. You record into the button the word associated with the action you want by pressing the button, after recording press the button again and you will hear the command you recorded.
For size I put it in my hand but must add, my hand is larger than the average female hand. Hope it gives you reference for size.
Place them spaced sporadically on a rubber mat and give a command that you want and press the button until they learn association with it.
It’s designed to develop a verbal communication with your dog.
This was developed with scientists attempting to determine the cognitive abilities of dogs to communicate with us.How Bunny the dog is pushing scientists’ buttons