This page is a DRAFT.
These are the units that are built into the firmware. They cannot be uninstalled or replaced because the base system requires them for certain operations.
If you are looking for the rest of the factory-installed units then please refer to:
The ER-301 firmware is open-source and has an SDK for developing your own units and publishing them as packages. Many user-contributed packages can be downloaded from the ER-301 Hub, a site run by the ER-301 community.