Circular Slim Ring review: A failure to execute

The list of best smart rings keeps growing, and with Samsung’s Galaxy Ring entering the market, there’s more interest in smart rings than ever before. These devices are a great way to track your health and sleep, especially when you find a smartwatch uncomfortable or don’t want a display disturbing your sleep.

The Circular Ring Slim smart ring promises to do all these things and then some. A more affordable and basic version of the Circular Ring Pro, it’s designed to be worn 24/7 and offers a treasure trove of data about your heart rate, breathing, temperature, SpO2 blood oxygen levels, sleep, and steps, to name a few. It also has the only vibration motor on a smart ring, setting it apart from the competition.

Sadly, the Circular Ring Slim has many problems that make it difficult to recommend. Many of these could be fixed relatively easily, but, for now, there are better smart rings to buy.

Price, availability, and specs

The Circular Ring Slim is available via Circular’s website and comes in sizes 6 to 13. I found the sizing to be slightly bigger than the Oura Ring; I’m a size 12 Oura Ring and a Size 11 Circular Ring Slim.

The Circular Ring Slim comes in two models: one with the vibration motor and one without. The light model (without vibrations) costs $234, whereas adding the vibration motor increases this to $294. Shipping to the US adds $9 in Route Package Protection and a $21 shipping charge.

It’s expensive — even more than the Oura Ring — and as you’ll read below, it doesn’t live up to its incredible promise.

What’s good about the Circular Ring Slim?

Many features with no subscription

I really wanted to like the Circular Slim Ring. It offers many great features and is slimmer than the Circular Ring Pro that came before it. It tracks seven core metrics and 142 total health metrics based on the data from those core metrics. It works with iOS and Android and offers a suite of features comparable to the Oura Ring, with a smaller and sleeker body.

I was pleasantly surprised by the sheer wealth of data that the Circular Ring Slim app collects. It has one of the largest datasets of any wearable device, and — assuming you can get past the clunky app — the information is laid out simply, predominantly offering scores to help you understand how good or bad the results are. Once you look past the battery life and the myriad of connectivity and sync issues, the data is on par with the competition. Having tested the Circular Ring Slim against the Oura Ring, a Whoop band, and my Galaxy Watch Ultra, I found that the sleep metrics were more or less on par with the competition.

At a weight of approximately 2 grams, it’s one of the lightest smart rings on the market. I casually played with it when I wasn’t paying attention, making it almost akin to a fidget spinner on my finger. If you have attention issues or need something pleasing to calm stress, the Circular Ring Slim is great to have on your finger.

The flat lip at the bottom of the Circular Ring Slim’s interior also makes it super comfortable to wear for long periods. This is because the device rests naturally on the finger with its flat edge; I found it to be more comfortable than the Oura Ring Gen 3. It’s one of the most comfortable rings I’ve worn.

I really enjoy having a vibration motor on my finger. It’s a great accompaniment to my morning alarm and a helpful way to do much more. You can set vital alerts to vibrate when your heart rate goes too high or too low, medication reminders, and guided breathing sessions. It can also gently wake you with different vibration patterns while you’re in a light sleep, and I found this worked reasonably well when I felt it.

Unlike many rings – but much like the new Samsung Galaxy Ring – the Circular Ring Slim offers all these features at one price without a subscription. This makes it incredibly compelling, considering it’s priced similarly to the Oura Ring without needing an ongoing subscription. However, it remains to be seen how this affects the rollout of new features in the future, and Circular wouldn’t confirm that it won’t launch a future subscription.

What’s bad about the Circular Ring Slim?

A failure to launch

When it comes to smart tech, there are a few things I expect at the minimum. The Circular Ring Slim delivers the basics on the health side, but it fails when it comes to syncing that data with your phone. Simply put: syncing the Circular Ring Slim with your phone is an exercise in complete frustration and a surefire way to increase stress levels.

To understand the flaws, you need to know how it should work. Your smart ring syncs directly to your phone, and it should take under a minute to update your app with all the data since your last sync.

Circular took a different approach. The Circular Ring Slim connects to your phone, then talks to the cloud, then talks back to your phone, and then the sync begins. The app displays this process and then begins syncing. To sync a day’s worth of data took over two minutes, primarily due to consistent connection issues. In one particularly egregious sync, the Ring disconnected seven times, and sadly, it always disconnected at least a few times. This is while the Circular Ring Slim is in Performance mode; when you switch to the light mode, it disables many of the core health features that you’re most likely looking for.

Beyond the sync issues, the app is also incredibly confusing. The main page asks questions to help the Ring understand your habits and calibrate the data but doesn’t make it clear you need to swipe (every time you open the app) to see valuable data. It also offers shortcuts to things like Sleep Analysis via a story-like layout at the top of the app called Circles.

Even after the app “successfully” syncs, it fails to display data like Energy Scores or Sleep Scores. It doesn’t track sleep fully or properly and won’t recognize a nap, so if you wake up and then go back to sleep, it thinks you only slept for a few hours.

Beyond the technological problems, the Ring Slim shows signs of wear and tear pretty easily. Within a few days, I noticed a few marks on the device’s exterior. This means it quickly loses its premium allure, especially when my Oura Ring looks much better despite several years of use. This means you’re less likely to wear the Circular Ring Slim all the time for fear of damaging it, which affects the quality of the data captured.

Should you buy the Circular Ring Slim?

The Circular Ring Slim promises a lot, and when it works, it delivers on this promise with an outstanding amount of data. My issue comes down to its inability to sync easily with your phone and just how frustrating the experience can be.

When trying to run the first update out of the box – which I highly recommend you do as it resolved many of my initial concerns – the update failed several times. Once it worked, the performance improved considerably, but the syncing issues persisted. So, it’s incredibly hard to recommend, at least until Circular resolves these issues.

Once it does, I think the Circular Ring Slim could be a fantastic smart ring for many. The vibration motor is unique, and it captures a ton of data. I haven’t been able to collect 14 days of data to fully calibrate the ring (despite wearing it for nearly two weeks), so I have yet to receive the personalized recommendations that are also included for free.

Unfortunately, I have to judge the Circular Ring Slim as it is now: the issues are too prevalent, and the competition is far too fierce to make it a worthy option. If you want a ring that can vibrate and track all your health, then the Circular Ring Slim is worth considering. But for most, I recommend picking one of the other best smart rings.

Nirave is a creator, evangelist, and founder of House of Tech. A heart attack at the age of 33 inspired him to publish the Impact of Tech newsletter, which covers the best technology and its impact on mental, physical, and emotional health. Follow him on Instagram, Twitter, and LinkedIn for more.