This is exactly the type of cover than comes with normal Puck.js devices. It's Black ABS plastic with the Puck.js Logo on it.

If you've cut or screwed into your Puck's back cover or are trying to make your own beacon then you might want to get another one!

What is Puck.js?

Puck.js is an intelligent Bluetooth button. With the Espruino JavaScript interpreter on its internal ARM microcontroller, software can be uploaded, debugged and modified wirelessly from any modern computer or phone, making development of embedded devices significantly easier. It has built-in sensors, lights, infrared transmitter, GPIO, and can even control other Bluetooth LE devices.