Circular Ring Slim vs Oura Ring 4

At just 2.2mm thin and 2.0 grams, the Circular Ring Slim stands out as the only smart ring with an onboard haptic vibration motor—allowing it to wake you at your optimal light-sleep phase with a silent finger buzz and acknowledge tap navigation. Battery life in full Performance mode is a modest 2 to 3 days (up to 5 days in Eco mode), but its subscription-free Kira+ AI assistant and silent alarm give it a unique niche.

The Oura Ring 4 cements Oura's lead at the top of the smart ring category by replacing the Gen 3's raised interior epoxy domes with a fully titanium interior and recessed 0.3mm sensors powered by 18-path Smart Sensing PPG. Delivering up to 8 days of battery life and the industry's most refined sleep staging, daytime stress, and cardiovascular age insights, its only real drawback is the mandatory $5.99/month Oura Membership.