Buy the Colmi R09. It costs $4 more than the R02 at Colmi's store, and it's the one of the two with confirmed skin temperature. I wear the R09; the R02 side is from Colmi's specs and Gadgetbridge.
Buy the Colmi R09. At Colmi’s own US store it costs $59.98 against $55.98 for the R02, and for those $4 you get the one ring of the two that confirmed skin-temperature readings. Everything else that matters, battery, water rating, app and the missing subscription, is the same on both spec sheets.
The R02 makes sense in one case: a seller you trust has it for clearly less than the R09, and you don’t care about temperature. The R09 is wrong for anyone who isn’t sure of their ring size. That warning covers the R02 too, and it’s the reason my R09 lives on the wrong finger.
How I know
I bought the Colmi R09 myself and wore it for a week, day and night, next to my Apple Watch Ultra. It scored a 7. I have not used the R02.
For the R02 side, and for the R09 specs I didn’t measure myself, I used two sources, both checked on October 27, 2026: Colmi’s product pages for the R02 and the R09, and Gadgetbridge’s device notes for Colmi rings. Gadgetbridge is an open-source Android app that reads these rings without Colmi’s app, so its notes describe what the hardware actually reports. For how a product earns a score here, see how I test.
The two side by side
| Colmi R09 | Colmi R02 | |
|---|---|---|
| Price at colmi.com (Oct 27, 2026) | $59.98 | $55.98 |
| Marketplace sellers (my review, Oct 12) | $20 to $30 | Not checked |
| Battery (Colmi) | About 5 days typical, up to 15 days standby | About 5 days typical, up to 15 days standby |
| Battery in my use | About a week, with short top-ups in the case | Not tested |
| Battery capacity (Colmi) | 14mAh; 18mAh for size 11 and up | 15mAh; 18mAh for size 10 and up |
| Weight (Colmi) | About 3.5g (size 11) | About 3.6g (size 7) |
| Sizes in Colmi’s store | US 7 to 13 | US 7 to 12 |
| Water resistance (Colmi) | 5ATM | 5ATM |
| Bluetooth | 5.2 LE | 5.2 LE |
| Skin temperature | Yes, confirmed by Gadgetbridge | Colmi lists it; Gadgetbridge doesn’t confirm it |
| App | QRing, no subscription | QRing, no subscription |
| Screen or vibration | None | None |
| Tested here | Yes, 1 week, score 7 | No |
The difference that decides it
Temperature. Colmi’s current product pages list “stress and temperature trends” for both rings. Gadgetbridge’s notes say something different: the R09 “has the largely same hardware as the Colmi R02” and “in addition, this device supports temperature measurements and gestures.” Its feature list marks temperature sync for the R05 and R09 only.
When the maker’s page and the people reading raw data off the ring disagree, I trust the second. That’s my judgment, and Colmi may have updated the R02’s hardware since Gadgetbridge last tested it (firmware 3.00.06 through 3.00.17). Until someone shows an R02 logging temperature, treat that line on its spec sheet as unconfirmed.
If you’re buying a ring for sleep, the R09 is the one with temperature for certain. For $4, that settles it.
What the R09 did on my hand
On the five nights it stayed in place, the R09’s sleep duration and timing in the QRing app lined up with my Apple Watch Ultra. I expected “close enough for $20.” It was closer than that.
The battery never ran out. I put it in its charging case for a few minutes while I showered, and that kept it going all week. Colmi rates it at about 5 days, so my week came from those top-ups.
The other two nights, the data was garbage. My ring slid on my pinky and the sensors lost contact with skin. That’s the sizing problem, and it’s the biggest risk with either ring.
There are no alerts. Neither ring has a screen or vibration, so nothing tells you the battery is low. I didn’t test steps, so I can’t tell you how either counts them.
Sizing: the same risk on both
I measured my index finger with Colmi’s sizing guide and ordered a size 11. It doesn’t go on my index finger on either hand. There was no sizing kit in the box, so the ring went on my pinky with a silicone adjuster, and it still slides at night.
Colmi now has a free online ring sizer on its site. You calibrate it with a credit card held to the screen, then measure a rigid ring that already fits the finger you want. I haven’t used it, so I can’t tell you whether it beats the guide that got me wrong. A physical ring sizer from any jeweler is still the safer bet. The R02’s sizes stop at 12 in Colmi’s store, so if you measure a 13, the R09 is your only option of the two.
Who should buy the R02
Buy it if you find it from a seller you trust for clearly less than the R09, and sleep duration, heart rate and SpO2 are all you want. On paper it does everything else the R09 does. I haven’t worn one, so that’s a spec-sheet call.
Gadgetbridge has tested the R02 on three firmware versions (3.00.06, 3.00.10 and 3.00.17) and rates both rings “highly supported.” If you want to skip Colmi’s app entirely on Android, either ring works. The R09’s gestures don’t work in Gadgetbridge yet.
Who should skip both
Skip both if you want notifications, a screen or anything that buzzes. A watch does those jobs. Skip both if you’re guessing your size.
If a $20 to $60 ring proves you’ll wear one every night, the next step is a better ring, and my sleep tracker guide covers that. My pick there is the RingConn Gen 3 at $349, with no subscription.
My recommendation
Buy the R09. The price gap at Colmi’s store is $4, the spec sheets match on battery, water resistance and app, and the R09 is the one with temperature confirmed by people who read the data off the ring. It’s also the one I’ve worn, and on sleep it kept up with a watch that costs 40 times more.
Measure your finger with a real sizer before you order either one. A loose ring is a bad tracker.
FAQ
Should I buy the Colmi R09 or the R02?
The R09. It costs $59.98 at Colmi’s store against $55.98 for the R02, and Gadgetbridge confirms it records skin temperature. Colmi lists temperature for the R02 too, and Gadgetbridge doesn’t confirm it. I wear the R09; I haven’t used the R02.
What is the difference between the Colmi R02 and R09?
Gadgetbridge says the R09 has largely the same hardware as the R02, plus temperature measurement and gestures. Colmi lists the same 5ATM water rating, Bluetooth 5.2, QRing app and about 5 days of battery for both. The R09 comes in sizes up to 13 in Colmi’s store; the R02 stops at 12.
Does the Colmi R09 need a subscription?
No. The QRing app shows sleep, heart rate and the rest with no paywall. The same app runs the R02.
How long does the Colmi R09 battery last?
Colmi rates it at about 5 days with typical use. Mine lasted about a week because I topped it up in the charging case for a few minutes while I showered.
Is the Colmi R09 accurate for sleep?
On the five nights it fit properly, its sleep duration and timing matched my Apple Watch Ultra. On the two nights it slid on my finger, the data was wrong. Fit decides accuracy, so get your size right.