You can use up to 6 Mesh units simultaneously in your Mesh network.
The main one connected to your internet box and the 5 others paired via WPS to the main Mesh unit.

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Warning: For a maximum coverage put the mesh units in the rooms where the Wi-Fi signal is low or
where there is no coverage.
Please refer to How should I organize my Mesh Network to optimize my Wi-Fi network? to have a proper installation.