COLMI R02 vs R03 Smart Ring: What Is the Difference?

The COLMI R02 and COLMI R03 are the two entry-level smart rings in the COLMI lineup, and at a glance they look nearly identical. Both track heart rate, SpO2, sleep, and activity. Both have the same stainless steel construction and IP68 waterproofing. Both connect to the same Da Fit app. So what's actually different between them — and does it matter enough to affect which one you should buy?

This comparison breaks down every difference between the R02 and R03, explains who each one is best suited for, and gives you a clear recommendation.

Key Difference: The Charging Case

The single most important difference between the COLMI R02 and R03 is the portable charging case included with the R03.

The R02 charges directly via a magnetic USB cable. When the battery is low, you remove the ring, attach the charging cable to the back, and plug it into a USB power source. This is a standard charging method used by most smart rings and works perfectly well at home or at a desk.

The R03 comes with a compact charging case that has its own built-in battery. You drop the ring into the case, the case charges it wirelessly, and you charge the case separately via USB when needed. The case holds enough power to charge the ring multiple times before it needs replenishing from a wall outlet.

This difference matters most in two scenarios:

• Travel: With the R03, you can charge your ring in your bag, on a plane, or in a car without needing a USB socket. This is a significant convenience for frequent travellers.
• Daily convenience: Dropping a ring into a case is faster and less fiddly than attaching a small magnetic clip to the back of a tiny ring every time it needs charging.

Health Tracking: Identical Features

Both the R02 and R03 offer the same health monitoring capabilities:

Heart Rate Monitoring

Continuous 24/7 optical heart rate monitoring tracks your pulse throughout the day and night. Both rings use the same sensor technology, positioned on the inner surface of the ring where it contacts the finger. Readings are stored in the Da Fit app for historical analysis and trend tracking.

Blood Oxygen (SpO2)

On-demand SpO2 measurements are available on both rings via the companion app. Blood oxygen saturation is measured using red and infrared light — the same technology used in clinical fingertip pulse oximeters, though at consumer-grade rather than medical-grade accuracy.

Sleep Tracking

Both rings automatically detect sleep and track light, deep, and REM stages throughout the night. A morning sleep quality score and timeline are provided in the Da Fit app. Sleep tracking is one of the strongest use cases for both rings, as the comfortable finger-worn form factor makes overnight wear natural and easy.

Activity Tracking

Daily steps, estimated calorie burn, and active distance are tracked automatically on both models. The accelerometer detects movement patterns and classifies them accordingly. Neither ring has dedicated sports modes like a smartwatch, but both capture the essential daily activity data that most users care about.

Menstrual Cycle Tracking

Both rings support menstrual cycle tracking through the Da Fit companion app, allowing female users to log and monitor their cycle alongside their continuous health data.

Design: Nearly Identical

The R02 and R03 share the same fundamental design — smooth stainless steel outer surface, polished inner surface, and a clean, minimalist aesthetic that looks like a piece of jewellery rather than a technology product. Both are available in similar colour options (Black and Gold) and the same size range (8–12).

The only aesthetic difference is the charging case that comes with the R03, which is a compact cylindrical or rectangular carry case that stores the ring when not in use. The case itself is smartly designed and adds to the premium feel of the R03 package.

Battery Life

Both rings deliver similar battery life from the ring itself — approximately 5–7 days under typical use with continuous monitoring enabled. The R03's charging case effectively extends the time between mains charges, since you can top up the ring from the case multiple times before needing to plug in the case itself. For travel purposes, this can extend total usage to 2–3 weeks between visits to a wall outlet.

Price Difference

The R03 typically costs slightly more than the R02, reflecting the additional value of the charging case. The premium is modest — usually in the range of £3–5 — which most users find easy to justify given the genuine convenience improvement the case provides.

COLMI R02 vs R03: Head-to-Head Summary

Feature	R02	R03
Charging method	Magnetic USB cable	Charging case + cable
Heart rate	24/7 continuous	24/7 continuous
SpO2	On-demand	On-demand
Sleep tracking	Light/Deep/REM	Light/Deep/REM
Steps/Activity	Yes	Yes
Waterproofing	IP68	IP68
Battery life	5–7 days	5–7 days + case
Sizes available	8–12	8–12
Companion app	Da Fit	Da Fit
Price	Lower	Slightly higher

Which Should You Buy?

Buy the COLMI R02 if:

• You mainly wear your ring at home and have easy access to USB charging
• Budget is your primary concern and you want the lowest possible price
• You're comfortable attaching a small magnetic charging clip to the ring

Buy the COLMI R03 if:

• You travel frequently and want to charge your ring without a wall outlet
• You value the convenience and tidiness of a proper charging case
• The small additional cost is not a concern
• You want a more complete, premium-feeling package

Our Recommendation

For most buyers, we recommend the COLMI R03. The portable charging case is a genuine quality-of-life improvement that makes the ring easier to charge consistently — and consistent charging means consistent health data. The small price premium is easy to justify for the added convenience. If budget is genuinely tight and you primarily charge devices at home, the R02 delivers identical health tracking at a slightly lower cost.