Smart rings are all the rage. Ever since the Oura Smart Ring was announced, they have become a sort of status symbol for health, wellness, and fitness fanatics. Now with more models coming to market, including the latest Samsung Galaxy Ring, they are gaining renewed attention. I have been testing the Circular Ring Slim through the summer, and while I didn’t initially get the appeal of wearing a smart device on your finger, I’m a member of the smart ring club now. With that said, this device isn’t perfect. But it gets a lot right.
What Is The Circular Ring Slim?
The Circular Ring Slim purports to be the thinnest and lightest smart ring on the market, and one of the first (if not the first) to incorporate haptic navigation and alerts. As every device does nowadays, it also has some AI features: it works alongside an AI wellness assistant named Kira+ that asks questions, assesses behaviour and stats, and makes recommendations over time.
The Ring itself can assess seven biometrics and 142 derived markers to help you both live and sleep better. The focus, says the company, is on “personalized, preventative health.”
With a matte black titanium shell, it measures 2.2mm and weighs 2 grams. It has a three-axis accelerometer that assesses activity and movement, and a surface temperature sensor. Advanced PPG sensors combine three LED light wavelengths – green, red, and infrared – to capture health vitals like heart and respiratory rates, blood oxygen levels, and heart rate variability.
It claims to offer a six-day battery life (more on that below) and 20 days of on-board memory. It collects health data every two minutes and, over time, helps build a picture of overall health as well as predict potential health conditions.
What does it capture? During the day, it tracks activity, blood oxygen levels, energy levels, calories burned, heart rate, respiration rate, and chronotype, among other metrics. At night, the ring tracks circadian rhythm and records sleep quality, heart rate variability, sleep disturbances, REM cycles, and sleep and wake times. Its sensors measure temperature variations during sleep, which, combined with other biometrics, can provide a clearer picture of immune systems and provide early detection of the onslaught of illness, Circular claims.
Haptic vibrations can be used to emit light vibrations when you set an alarm clock to wake you up in the morning, as well as for medication reminders and guided breathing exercises with prompts to inhale, hold, and exhale.
After a 14-day calibration period, Kira+ begins to provide personalized health information and recommendations to guide you through your day. She continues to analyze you as you continue to wear the ring and tweaks recommendations and guidance accordingly.
To help you make actionable sense of the wealth of data collected by the new slim version of the Circular Ring is Kira+, an AI-powered conversational health and wellness assistant. Kira+ is trained with millions of health data points and leverages the latest generative AI language models. It provides personalized health information and recommendations based on the data the ring collects about you from one day to the next, along with baseline figures.
The Circular Ring Slim started shipping in December 2023 and is priced at $403 in Canada for the version with haptic vibrations or $332 without, so about the same as a premium smartwatch or activity tracker.
Circular Ring Slim Review
First off, I can’t stress enough the importance of ordering a sizing kit before buying this, or any smart ring, especially if it’s the first one you are using. My review sample is a tad too big (your finger size will fluctuate slightly throughout the day) though it fit well enough to accurately track my stats with the sensors touching my skin. You should wear it on the index finger of your non-dominant hand or, as secondary options, your middle or ring finger.
The Design and Wear
It’s comfortable to wear all day and overnight, though you might want to remove it while doing certain activities. I found that it could get in the way while washing my hair and face, for example, putting on make-up, and washing dishes. It can also get in the way when lifting weights unless you position them in such a way that they don’t push the ring against your finger. Remember, it’s thicker than a traditional ring.
With an IP68 rating, this Ring is durable, and I unintentionally tested just how durable. Because my sample was slightly too big, it ended up sliding off my finger a few times (three, to be exact!) when I was loading the washing machine. I noticed after about 20 minutes each time, thankfully before the spin cycle began, and I was able to rush to the machine, pause the wash, and search for it inside the drum. Each time, I crossed my fingers and synced the ring in hopes that I didn’t ruin it. I was pleased to see that it worked every time. While I wouldn’t recommend washing the ring, I’m confident to say you can safely swim in fresh water with it.
Over my extensive review period, however, I did notice some scuffs and scratches on the underside, some of which can be attributed to those mishaps. Nonetheless, they’re minimal, but expect that this ring will show some wear and tear over time.
In terms of battery life, there are two modes: Performance Mode and Eco Mode. The latter supposedly extends battery life to up to eight days by using low-frequency acquisition and eliminating sleep stages. Most people will want to use Performance Mode to get the most out of it, and this drastically reduces battery life to a rated 2.5 days. I’d say it’s closer to 1.5-2 days: I charge it daily.
It does come with the cute USB-C charger you can plug right into the side of your laptop and charge while you work away. It charges quickly, so you’ll be back up and running in no time. I just wish it came with a charging case. The charger does have a little keyring, though, so you can attach it to your keys and bring it with you. There is a longer charging cable available for purchase separately as well.
It’s All About the App
The Ring Slim requires a 14-day calibration period where it will capture data to determine your baseline figures for things like heart rate, body temperature, stress, and more. The Kira+ wellness assistant, currently in beta, will ask questions each day to get to know you and your habits a little better. These range from basic questions like how often you work out or if you take naps to puzzling ones that don’t make much sense and may have been lost in translation. Nonetheless, I answered them all to the best of my ability and started to get the full experience after the two-week calibration period was done.
From there, I was impressed with not only the data, but also the feedback. It measures sleep, energy, stress level, and vitals like heart rate and blood oxygen. With sleep, you get more than the typical duration, stages, and sleep score, but also in-depth data like disturbances, tranquility, circadian rhythm, sleep debt, and heart rate during sleep.
I compared data with my Apple Watch, which I continued to wear on my wrist, and found that the numbers usually fell in line well with one another, with slight variations. The Circular Slim Ring would often suggest I burned more calories and had a higher heart rate than the Apple Watch for workouts. But sleep data was often almost identical with slight differences in the stages.
At any moment, you can take a live measurement of your vitals by placing your hand up to your chest, making a fist, and holding it there for 15 seconds. This is a great way to do a quick check if you feel like your heart rate might be up or you’re stressed. If so, you can activate a guided breathing session, which uses haptic feedback on the ring to vibrate as you breathe in and out.
Haptic feedback can also be used for a wake-up alarm or medication reminders. Set these up in the app at the dates and times you prefer and you’ll get a slight vibration to notify you. Snooze or stop the alarm by tapping on the logo at the top of the ring. While the feature is technically for medication reminders, you could theoretically use this as a modern-day version of a rubber band around your finger to remind you to do everything from water the plants to put the roast in the oven or check on the neighbour’s cat every day at 4 p.m. while they’re away on vacation.
One major issue with the app is that it either fails to sync to the ring or takes forever to do so. At times, the app crashed repeatedly and I had to delete it and re-install it on my phone to get going again. Each time this happened, while much of my historical data was retained, all the recorded sports sessions were wiped. There have been several firmware updates since I started wearing the ring, and I have noticed an improvement since. I still run into slow syncing issues from time to time, and the app sometimes doesn’t load, requiring that I delete it, re-load, and start over again. I’m hopeful, however, that the company is continuously improving the experience.
How Does Kira+ Work?
The daily recommendations from Kira+ are useful. They take into account all the data points the ring acquires over time, particularly the night before, to generate a report for you. For example, one day, she might tell me that my energy score is low, mainly due to heart rate variability and breathing rate, and provides recommendations on how to improve it like yoga or meditation and deep breathing exercises. At one point, she even recommended that I add supplements like BCAA, zinc, and magnesium to my diet to help with body recovery, which was low.
Each morning, she also provides a list of items from which to choose that might have impacted your sleep. This could be alcohol, blue light late in the evening, or a late bedtime and relate this to results. For example, on a morning when I indicated that I had a glass of wine and was on my computer late in the evening, she suggested that this may have impacted by tranquility during sleep. Her suggestion was to either reduce screen time before bed or use a blue light filter.
While some of the advice can get repetitive, she does provide more and more detail as you go along. There are also helpful notifications reminding me when it’s the optimal time to do a workout or go for a walk, eat a meal, or even head outside and get some Vitamin D.
There are Circular Coins with Kira+ that you earn by reaching health and activity goals. These are supposed to be digital currency that you can exchange for products and services from both Circular and third parties, as well as premium app features. But this isn’t ready for primetime just yet. Right now, you accumulate these coins and you’re asked, “what can this mean?” The answer is I don’t know and nor does Circular just yet. But it’s a sign of some potentially fun things to come.
Should You Buy the Circular Ring Slim?
The Circular Ring Slim is a decent, albeit expensive, option in the smart ring space. While Oura is the favourite of many, it’s also slightly more expensive. The biggest differentiator is that Oura Ring requires a subscription to get the most out of it. You don’t need a subscription with the Circular Ring Slim. If you own a Samsung Galaxy smartphone, it’s a no-brainer to get the new Samsung Galaxy Ring, which is also more expensive but will provide a more seamless and integrated experience, especially if you have a Galaxy Watch as well.
As far as third-party brands go, the Circular Ring Slim is worth considering. Given the price, I would have expected it to come with a charging case, offer better battery life, and have an app that wasn’t so buggy. I love the app when it does work and the recommendations and notifications from Kira+ have become something I look forward to each day. I appreciate the combination of notifications and daily recommendations I can read through once I sync and have time to generate the report. But slow syncing and app issues can make it a frustrating experience at times as well.
Unfortunately, I don’t think this smart ring is worth $400. Admittedly, smart rings are such a new category (Oura excepted) and they have to pack a lot of features into such a small size. This requires a lot of intricate manufacturing not to mention R&D, which results in a high cost in general. But for this price, I expect more.
If Circular can somehow bring down the price and add a charging case or you can find an awesome sale, and firmware and app updates continue on the right path, Circular might be onto something with the Ring Slim.