This $350 Oura Ring 4 Tracks Your Sleep. Is It Worth the Splurge? The New York TimesWhy is everyone wearing the Oura Ring? Vox.comWhy the Oura Smart Ring Has a Cult Following The Wall Street JournalOura Ring 4 review: still on top — for now The VergeThe Oura Ring 4 is sleek and easy to wear but scratches easily. Here’s what it’s like CNBC