I recently made a batch of these keychains. I made a 3 layer build with acrylic in the middle and a space cut out of the back and middle to insert and led diode with a coin cell battery. Could also be used for a necklace or keychain. The cow moves freely inside the acrylic box i put him in. Took one of my credit card style business cards to cut a thin back plate to swivel to the side to remove the battery, turn off the keychain, change the light, etc. I will be experimenting with more items of this style.