Furuno's HUB101 is designed for the NavNet 3D and TZTouch/TZTouch2 system and allows for information to flow seamlessly from one unit to another. The HUB101 is required if you are going to have more than two Ethernet Devices on the NavNet 3D or more than 1 Ethernet Device on the TZTouch or TZTouch2 Ethernet System.