Circle is by far one of my favorite solutions for devices inside of your home.
It is simple to use, setup, and compact.
The only downside is that they are only available via secondhand market (eBay). Luckily they are fairly low cost.
Why did they stop making them?
Circle was acquired by Aura in December of 2021. In doing so they merged their solution with Aura.
Where can you purchase?
eBay is the best place I have found to still purchase.
https://www.ebay.com/sch/i.html?_nkw=circle+gen+1+parental+control&_sop=12&_kwlnd=1
TMGT 