Does anyone know if the UNAS range uses ZFS as well or does it use BTRFS or something else? I only know their higher end enterprise range specifically said ZFS

Does anyone know if the UNAS range uses ZFS as well or does it use BTRFS or something else? I only know their higher end enterprise range specifically said ZFS but all the others doesn't seems to mention it. And I really wish there is a simple 4 bay ZFS NAS.