Circular Ring Slim sheds the timber to offer a thinner alternative to the Oura Ring

The new slimline ring barely registers on the scales
Circular Circular Ring Slim launch
Wareable is reader-powered. If you click through using links on the site, we may earn an affiliate commission. Learn more

Smart ring startup Circular has returned with what it claims is the industry's thinnest and lightest offering yet - the $275 / £225 Circular Ring Slim.

The trimmed-down ring is the progression of the company's Circular Ring Pro released last year, hitting the scales at just 2g and measuring 2.2mm thick. 

To put these specs into context, industry leader Oura's Generation 3 Horizon model measures in at 2.55mm thick and clocks the scales at around 4-6g, while the Circular Ring Pro is 2.75mm and 4g.

Plus, Circular indicates that losing some of the bulk hasn't had a detrimental effect on the array of sensors packed into the Slim.

The three-axis accelerometer is still present for fitness tracking, while the temperature sensor, PPG sensor, and LEDs that are used to monitor the likes of breathing rate, heart rate variability, blood oxygen saturation, and heart rate are sticking around, too.

CircularCircular Ring Slim

Interestingly, despite that smaller footprint, battery life is also relatively superior. Circular claims that the Slim will last around five days on a single charge, though it's not entirely clear whether this includes complete 24/7 tracking with all features enabled.

Part of the reduction in size has seen the Pro model's button replaced by a haptic interface, with users able to tap anywhere on the ring to interact with it. New features like the smart alarm, as well as breathing and mindfulness exercises, are also boosted by vibrations on the ring.


Away from the ring itself, Circular is also the latest to introduce AI to the experience. It notes that the Slim will sync with Kira+ - an AI assistant focused on health and wellness - in order to better understand the user's habits and biomarkers. 

Unlike Oura (and others), the Circular experience is also available without a subscription - with the Ring Slim able to be pre-ordered now for $245/£199 before officially going on sale on 15 December. From then, it will be available for $275 / £225.

It's one we're very eager to test out and compare to the rest of the burgeoning smart ring market.

How we test

Conor Allison


Conor moved to Wareable Media Group in 2017, initially covering all the latest developments in smartwatches, fitness trackers, and VR. He made a name for himself writing about trying out translation earbuds on a first date and cycling with a wearable airbag, as well as covering the industry’s latest releases.

Following a stint as Reviews Editor at Pocket-lint, Conor returned to Wareable Media Group in 2022 as Editor-at-Large. Conor has become a wearables expert, and helps people get more from their wearable tech, via Wareable's considerable how-to-based guides. 

He has also contributed to British GQ, Wired, Metro, The Independent, and The Mirror. 

Related stories