TheCircular Ring Slimis a smart ring that tracks almost as much as a smartwatch yet fits into the slimline package of a ring. It features up to five days of battery, customizable tracking metrics, fitness suggestions, sleep analysis, and more in a ring-sized package—which is undeniably cool in terms of tech.
I’ve spent more than a month using the Circular Ring Slim daily. While there are some reasons you might consider adding it to your health-tracking hardware, there are far more reasons why you should steer clear of this underbaked product.
Circular Ring Slim (2024)
The Circular Ring Slim packs heaps of tech into a ring-sized package, allowing you to track your vitals, activities, and more. It’s comfortable, comes in a range of sizes, and looks decent enough. The Circular app provides heaps of data and insight into your health, fitness, and sleep, though is a bit cluttered. Furthermore, issues with battery life and connectivity can make using the Circular Ring Slim problematic.
A Slimmed Down, Sturdy Design Packed With Tech
I’ll caveat all of this review by saying I don’t have the biggest hands. There, I’ve said it.
Still, although the Circular Ring Slim is the second generation, it’s still a little chunky in size. At least, it is for me, especially compared to my wedding band, which is very slim. Still, the Circular Ring Slim has to hide its extensive array of tech somewhere. Considering the Ring Slim weighs just 2g and is only 2.2mm thick, it’s a great piece of engineering.
It comes in standard ring sizes 6-13, which you select during the purchase process. However, if you’re unsure about your ring size, you can use theCircular Sizing Kitto figure out your size. I sized mine up as a 9, which is roughly the same as my wedding ring, but it came up slightly large.
On the underside of the ring is a larger, flatter protrusion that houses the battery and other sensors. Again, when you consider the size of the hardware we’re talking about here, the small area dedicated to the battery and other tech is absolutely fine.
The Ring Slim is only available in black. Although the Circular claims the Ring Slim was “forged in Mordor,” I reckon it was all probably constructed in France, where Circular is based. However, that doesn’t detract from its “medical grade non allergenic, non metallic and comfortable inner material,” which is an ultra-strong resin, and the exterior’s matte black aluminum and carbon fiber alloy.
The combination is strong. The Circular Ring Slim never feels like it will flex or bend, and there hasn’t been a moment during my use where it felt like the ring would suffer damage. All in all, it feels extremely well-built.
What I wasn’t so happy with was the number of scratches and chips the Circular Ring Slim picked up over a short period. Aesthetically, these small blemishes don’t bother me, but I’d expect the aluminum and carbon fiber coating to hold up to greater pressure. The scratches have all come from regular daily use; I’m not out mountain climbing every day or running parkour lines.
I’ve been using the ring for a while, and obviously, it will pick up some scratches here and there. But I’m concerned about how the Ring Slim might look in several months, especially once the summer starts, and I’m at the beach and more outdoors in general.
Limited Battery Life and Connectivity Can Be Difficult
Circular states that the Ring Slim can last up to five days on a single charge. I didn’t find this accurate in either of its two battery modes, Performance and Eco.
Switching the ring to Eco mode definitely enabled extra battery life by reducing the sampling frequency for its various sensors and disabling sleep stage information. Sleep tracking is one of the primary reasons I use smart tech, so having to switch this off to ensure the Ring Slim battery lasts for more than 36-48 hours isn’t particularly useful.
Sure, you may switch between the modes, but that’s not particularly useful when you just want to set and forget. Of course, the answer is remembering to charge more frequently, and the Ring Slim smartphone app (more on this in a moment) sends battery notifications reminding you to charge.
As you might expect, you connect to the Ring Slim using Bluetooth. The connection process is simple enough, but there are issues around connectivity once you get going.
For example, on a couple of occasions, I couldn’t get the ring to connect to my smartphone. The Ring Slim wouldn’t register in the app or connect for multiple days and only connected again after being left on the charger for hours at a time. I had to delete the Ring Slim each time, then restart the sign-up process, losing heaps of tracking data. Although the Ring Slim is meant to hold data for up to 20 days before syncing, the fact it wouldn’t connect under any state forced me to lose data.
At the time of review, the Circular Ring Slim has been sitting on its charging cradle for days, not responding. I can’t factory reset it because it doesn’t connect to my phone, and an update has seemingly broken the haptic vibration function, so I have no idea if it’s responding to my inputs. It’s just not very good.
Decent Tracking Accuracy But Some Inaccuracies
Of course, the main reason to wear a smart ring is to track your vitals, such as sleep, fitness, heart, and more. The Circular Ring Slim tracks your heart rate, breathing rate, temperature, blood oxygen levels, activity, sleep, and more. It’s a similar range to other smart rings (and other smart tracking devices).
When you start using the Circular Ring Slim, you must wait a full 14 days for its calibration period to complete. That sounds like a long time, but all smart rings have a calibration period to enable accurate measurements and feedback. During this calibration period, the Ring Slim and Circular’s AI tool, Kira, is learning all about you and preparing to give you tailored advice.
To keep tabs on the accuracy of the Circular Ring Slim, I’ve been comparing its data to an Amazfit Balance smartwatch. For the most part, the measurements roughly align, but I also noticed some big discrepancies, especially regarding step tracking.
I saw differences of thousands of steps between my watch and the Ring Slim. Now, I’m not sure whether that’s down to the tech or other factors like me tapping the keyboard all day or banging on my steering wheel while driving, but there was often a major difference.
That said, the sleep tracking data between the Amazfit Balance and Circular Ring Slim was largely accurate, which is positive.
The data tracking for your activities is also just that: tracking. It’s useful, but you don’t have the same in-depth location data you’ll get with other smart devices. It’ll measure your steps in general, but it is frustrating without a specific setting for tracking exercise.
Easy-to-Use App With Too Many Notifications
The Circular app is simple enough to use, with an interface filled with—you guessed it—circles! As the Ring Slim has no interface, you’ll spend a decent amount of time here.
There are tracking circles for your alarm clock (which also vibrates the ring), Sleep Analysis, Energy Analysis, Live Measurement, and Stress Levels, with other options also available, like the Medication Reminder. Under the circular menus, you can easily switch between data modes and glance at some data types, such as steps, daily cardio points, and so on.
It’s a simple-to-use interface, but it’s not the best, as it can start to feel cluttered once the notifications and suggestions begin to roll in. You can switch some of these off, but once Kira gets going, the suggestions regarding what you should be doing or how to tweak your behavior stack up.
On that, the number of overall notifications from Circular is too high, especially as they’re repetitive. Reminding me that there is a specific good time for me to drink caffeine at the same time every day was irritating, especially as I don’t drink coffee and I sup a regular flow of tea throughout the day. So, repetitiveandpointless; the winning combo.
Circular Ring Slim: Great Idea, But Needs Work
It’s a difficult time for theCircular Ring Slim. It wasn’t the first smart ring to market, and it’s now being caught up by new releases, like the Samsung Galaxy Ring, as well as competing with leading alternatives like the Oura Ring 3.
Even with endorsements from former F1 driver Romain Grosjean, I’ve found issues during my time with the Circular Ring Slim.
There are numerous positive sides to the Circular Ring Slim. It’s comfortable, fits well, and looks pretty good. While the tracking of activities could be a little more in-depth, sleeping tracking and other fitness metrics are accurate. In addition, the Circular app could use some work and streamlining, but it’s easy to use and has room to grow.
On the other hand, the connectivity issues I experienced have made using the Ring Slim tricky, and you’d hope the coating would be more scratch-resistant. As said, I’m still waiting for the Ring Slim to come back to life, without knowing if it is dead or not.
Retailing for $275, it’s hard to recommend the Circular Ring Slim to anyone but the most ardent supporters of smart tech who want to try everything and anything.
