BT has two products:
1) First is exclusive to their broadband customers with SmartHub where they are rented, and may be included in some packages, the discs are coloured black to match the SmartHub.. This is branded "BT Complete WiFi" and pictured here:
2) The second is a a retail product suitable for anybody, connects to any router via Ethernet, and competes with Eero, Google WiFi etc. This is branded "BT Whole Home WiFi" and there are at least three versions at different price points. All of these are coloured white, scroll down this page to the table, https://shop.bt.com/learnmore/bt-branded-products-an...
* Mini Whole Home
* Whole Home
* Premium Whole Home
The Premium uses a second 5 GHz channel for the link between the discs, rather than sharing, and hence why a lot more expensive.
It appears the BT Whole Home products are rare, most of the competition wants to replace your router, and connect to a modem. Easy if you are with Virgin Media, not as easy for other types.
PCPro magazine this month compares 19 different makes of mesh WiFi.
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