It is made of durable hard plastic and contains a receiver that is integrated into the lid of the box. The sliding lock, in combination with the sealing ring, prevents the box from accidentally opening in the water and keeps water from entering from the outside. A Gore-Tex valve on the back ensures that no excessive pressure builds up inside the box and is also waterproof. The battery box is secured to the eHarness with four screws. In our Help Center, we explain how to replace the box if necessary and what to keep in mind during the process.