REVIEW – Smart rings have been on my radar this year after my RingConn smart ring review, which I really enjoyed. Now, months later, I’ve had the opportunity to test another contender in the growing smart ring market. The Circular Slim smart ring promises to blend style with advanced health-tracking capabilities as an alternative to smart watches and other fitness wearables. In this review, I dive into the Circular Slim’s design, features, and performance to see if it deserves a spot on your finger.
What is it?
The Circular Slim is Circular’s second smart ring. It’s a wearable fitness tracker that can track your activity, including steps, stress, temperature, heart rate, breathing rate, HRV (heart rate variability), blood oxygenation, and sleep.
What’s included?
- Circular Slim smart ring
- USB-C Charging adapter
Tech specs
Click to expand Specs
Sensors:
1 infrared LED sensor
1 red LED sensor
1 green LED sensor
3 axis accelerometer
1 surface temperature sensor
Memory: Storage for up to 20 days of data without syncing
Waterproof: IP68 grade (the ring can be immersed in 5 meters of water for a maximum of 30 minutes)
Exterior: High grade alloy of matte black bead blasted aluminium and carbon fiber
Interior: Medical grade non allergenic, non metallic and comfortable inner material
Width: 8.8 mm
Thickness: 2.2 mm
Weight: 2 grams
Available in 8 sizes: From US 6 to US 13
Compatibility: iOS 11.0 or later and Android 6.0 or later
Design and features
Regarding styles, the Circular Ring Slim is only available in the black version you see here. The right is incredibly light weight and I was certain it was made of plastic until I started working on this review and checked the specs. That’s where I found that the outer shell of the ring is actually aluminum.
The inner surface of the ring has sensors and two electrical contacts that mate with the charging adapter. It has a unique inner shape that you can see above.
You can order a Circular Ring Slim in sizes from 6 to 13. I ordered mine to be worn on my non-dominant ring finger. Although this ring is slightly wider than the RingConn smart ring that I recently reviewed, I found it to be pretty comfortable, but unlike the wedding band that I wear on my left ring finger, I always know (feel) that it’s on my finger.
Charging the Circular Ring Slim requires the included USB-C adapter. This little adapter has a thin lanyard cord in case you want to attach it to a keychain for travel.
I just left it plugged into the USB-C port of the Baseus charger that I reviewed last year. When the smart ring is placed on the charger, it is held in place with magnets, and the LED on the end of the charger will “breathe” while charging.
I’ll talk about the battery life of this smart ring a little later in the review.
Initial setup and the Circular app
Like any fitness gadget, you’ll need to install an app on your phone. Getting up and running with the Circular Ring Slim smart ring isn’t difficult, but the ring will need to be calibrated for two weeks before the data becomes more accurate. During the calibration period, you will be asked questions.
Once fully calibrated, your fitness data is presented on the main page for the current day along with info for the current zone that you’re in. The Circular app isn’t difficult to understand or navigate, but I didn’t find it as visually appealing as the RingConn app. I realize that this is totally a matter of personal preference, though. I guess the main reason why I like the way RingConn presents the data is that it takes less scrolls and clicks vs. Circular. Otherwise, it’s all the same kinds of information.
With the Circular app, you have a row of circles at the top that you can tap to drill down into the details.
I wish that Circular was able to pull in my workout info from Apple Health so I could see info for specific workouts. Instead of being able to see my data for a walk or workout session, it’s displayed per day in a gauge type of layout.
Activity tracking
As far as how well the Circular Ring Slim tracks my steps, I found the number of steps to be significantly lower than that of my Apple Watch and RingConn ring. However, the Apple Watch and RingConn ring are worn on my left (dominant) hand, and the Circular Ring Slim has been worn on my non-dominant hand. So I did a test. I recorded the number of steps for the three devices after I’d been sitting for several minutes. Then I got up and walked around the house at my normal speed and counted out 150 steps, came back to my desk, waited a few minutes, and rechecked the totals. Here are the results. The first number is the total of steps already counted for the day for each device. The second number is the total number of steps after counting off 150 steps, and the third number is the difference.
Circular Ring Slim – starting step count 2114 / 2130 / counted 16 steps
RingConn – starting step count 3358 / 3496 / counted 138 steps
Apple Watch – starting step count 3127 / 3301 / counted 174 steps
Wow, as you can see, the Circular ring did a really terrible job counting my steps compared to the other devices. It wasn’t even close. I looked back through several days of tracking and found that the Circular ring recorded 1000-1500 less steps than the RingConn and Apple Watch.
Sleep tracking
When it comes to sleep tracking, I found that the Circular Ring Slim and RingConn ring’s information was really close to the same numbers as far as time awake, REM, and deep sleep during the night. I feel like I can trust the data for that metric.
The same goes for Blood oxygen, temperature and heart data. When I compared the numbers from the Circular ring, RingConn ring, and my Apple Watch, they were all close enough to the same numbers that I would trust the data coming from the ring.
It comes down to the step tracking being the worst metric, at least during my month wearing this ring. I was able to compare the step data from the Circular ring with the RingConn and Apple watch, and every day, it recorded significantly fewer steps.
Another tracker that I don’t really trust is the stress tracking feature. The app says that I’m anxious pretty much every day and I’m not. When I check the RingConn app, it tells me that I’m at a normal stress level. Go figure.
Other features worth mentioning
In addition to tracking fitness data, the Circular ring has a built-in vibration feature that can wake you up, remind you to take your medications at a certain time, and move you when you’ve been sedentary for too long. Note: You can buy the ring with or without the vibration feature.
The Circular app has built-in breathing exercises that also use the vibration feature. For example, there’s a box breathing exercise where you breathe in for 4 seconds, hold for 4 seconds, breathe out for 4 seconds, hold for 4, and repeat. The ring will vibrate at each 4-second interval.
The app also has an AI feature that suggests activities based on your fitness data. If it sees that you’ve been stressed a lot, it will suggest that you exercise more, etc.
However, since the app thinks I’m always anxious, I’m not sure I really trust that feature.
Circular Ring Slim battery life
The Circular webpage says that this ring has up to 5 days of battery life. I didn’t find this to be true. Here’s my charging log, where I compare it to the RingConn ring I was wearing on my opposite hand during the same time.
6/26 8:30am Charge Circular Ring Slim and RingConn ring to 100%
6/29 8:00am Circular ring at 5%
6/29 8:00am Charged Circular Ring Slim to full
6/29 8:00am RingConn ring at 59%
7/1 1:00pm Circular Slim low battery warning 9%
7/1 1:00pm Charged Circular Ring Slim to full
7/1 1:00pm RingConn at 36%
7/4 8:30am Circular Slim at 6%
7/4 8:30am Charged Circular Ring Slim to full
7/4 8:30am RingConn at 5%
7/4 8:30am Charged RingConn to full
7/7 8:00am Circular Slim at 5%
7/7 8:00am Charged Circular Ring Slim to full
7/7 8:00am Ringconn at 59%
As you can see from my unscientific tests, a fully charged Circular Ring Slim lasts for about 3 full days compared to the RingConn where a full charge lasts about 7-8 days.
You can improve the Circular Ring Slim’s battery life by changing the data mode in the settings from performance to eco. Eco mode does not utilize the Sleep Stage feature and has less frequent heart rate acquisition.
What I like about Circular Ring Slim smart ring
- Lightweight
- Built-in alarm/wake feature
What needs to be improved?
- Step tracking is abysmal and needs to be vastly improved
- Not sure I trust the stress track feature either
- Offer the ring in different colors
Final thoughts
I was hoping for a lot more out of the Circular Ring Slim, but since I’d already reviewed the RingConn ring and like everything about it including the long battery life, it’s tough to recommend the Circular ring because the battery life is worse, step tracking isn’t accurate, and stress tracking seems off the mark. Since the main metric that I like to keep track of is my activity / steps, I can’t recommend this smart ring.
Price: $234 (without vibration), $294 with vibration
Where to buy: Circular
Source: The sample for this review was provided by Circular. Circular did not have a final say on the review and did not preview the review before it was published.
