Circular Ring 2 3.0g Single-Lead ECG, FDA-Cleared AFib & Kira AI Titanium Smart Ring
3.0-gram titanium smart ring introducing on-demand single-lead Electrocardiogram (ECG) recording and FDA-cleared Atrial Fibrillation (AFib) detection on the finger, paired with 3-wavelength optical PPG, NTC skin temperature, 8-day battery life, wireless dock charging, and the subscription-free Kira AI health strategist.
Editorial Rating Methodology (★ 4.8 / 5.0): This score is an internal editorial evaluation compiled by the RECIWO Labs editorial team—not a user poll or crowd-voted rating. It assesses published silicon compute efficiency (25%), optical/sensor/actuator engineering (25%), battery & thermal envelope (20%), SDK/software openness (15%), and price-to-specification value (15%) based on official manufacturer datasheets and public technical documentation. Learn more about our evaluation rubric →
Key Engineering Highlights
- Brings clinical-grade cardiac electrophysiology to a 3.0-gram, 2.55mm-thin titanium smart ring—allowing wearers to capture a 30-second single-lead ECG trace by touching the outer ring bevel with the opposite hand to screen for Atrial Fibrillation (AFib)
- Eliminates the mechanical button and replaceable outer shells of earlier Circular generations in favor of a solid, IP68/5ATM waterproof titanium chassis that lasts up to 8 days per charge and recharges in 30 minutes wirelessly
- Synthesizes 140+ biometric parameters into personalized recovery, circadian, and stress recommendations via the onboard Kira AI Health Strategist with $0/month subscription fees
Full Hardware Specifications
| Processor / Edge SoC | Ultra-Low-Power Biometric Analog Front-End (ECG + PPG AFE) + ARM Cortex-M4F BLE Microcontroller w/ 16-Day On-Ring Memory |
|---|---|
| AI Model Stack | FDA-Cleared Atrial Fibrillation (AFib) ECG Classifier + Kira Conversational AI Health Strategist (Stress, Sleep & Energy) |
| Display & Optics | Screenless 2.55mm × 7.8mm PVD Titanium Exterior w/ Integrated Finger-Touch ECG Electrode & Hypoallergenic Inner Liner |
| Camera & Vision | None (IP68 & 5ATM Waterproof Construction Across Sizes 5–13 w/ Digital Sizing App Verification) |
| Measured Weight | 3.0g Average Weight (2.55mm Ultra-Thin Profile × 7.8mm Width in Obsidian Black, Silver, Gold & Rose Gold Titanium) |
| Battery & Runtime | Up to 8 Days in Power Mode / 5 Days in Continuous Performance Mode (Full Recharge in 30 Minutes on Wireless Dock) |
| Connectivity & I/O | Bluetooth Low Energy (BLE 5.2) + iOS & Android Circular App + Apple Health / Google Health Connect ($0/Mo Subscription) |
| Sensors & Acoustics | Single-Lead Dry-Electrode ECG Sensor + 3-Wavelength (Red/Green/IR) PPG Array (100Hz Sampling) + NTC Skin Temp + 3-Axis IMU |
⚖️ Side-by-Side Comparison: Circular Ring 2 3.0g Single-Lead ECG, FDA-Cleared AFib & Kira AI Titanium Smart Ring vs. AI Wearables & Audio Peers
Direct specification comparison against leading competing devices in the AI Wearables & Audio category.
| Specification | Circular Ring 2 3.0g Single-Lead ECG, FDA-Cleared AFib & Kira AI Titanium Smart Ring (Current) | PLAUD NotePin Pro Magnetic AI Memory Capsule → | Limitless Pendant 2 All-Day AI Clasp → | Omi DevKit 2 (Open-Source nRF5340 AI Necklace) → |
|---|---|---|---|---|
| Brand | Circular | PLAUD.AI | Limitless | Based Hardware |
| Retail Price | $349 | $179 | $129 | $89 |
| Editorial Rating | ||||
| Edge SoC | Ultra-Low-Power Biometric Analog Front-End (ECG + PPG AFE) + ARM Cortex-M4F BLE Microcontroller w/ 16-Day On-Ring Memory | Custom Dual-Core Noise-Canceling DSP + BLE 6.0 SoC | ARM Cortex-M55 + Ethos-U55 microNPU | Nordic nRF5340 Dual Arm Cortex-M33 |
| AI Model Stack | FDA-Cleared Atrial Fibrillation (AFib) ECG Classifier + Kira Conversational AI Health Strategist (Stress, Sleep & Energy) | Whisper-Large-v3 + Claude 4 / GPT-4o | Limitless Cloud Memory Engine | Custom Webhook / Local Whisper + Llama |
| Display / Optics | Screenless 2.55mm × 7.8mm PVD Titanium Exterior w/ Integrated Finger-Touch ECG Electrode & Hypoallergenic Inner Liner | Micro-perforated status LED + Linear haptic motor | Privacy Recording Status LED | Screenless + Programmable RGB Ring |
| Camera | None (IP68 & 5ATM Waterproof Construction Across Sizes 5–13 w/ Digital Sizing App Verification) | None | None | Optional OpenMV Camera Hat |
| Weight | 3.0g Average Weight (2.55mm Ultra-Thin Profile × 7.8mm Width in Obsidian Black, Silver, Gold & Rose Gold Titanium) | 22.0g | 17.5g | 14.5g |
| Battery | Up to 8 Days in Power Mode / 5 Days in Continuous Performance Mode (Full Recharge in 30 Minutes on Wireless Dock) | 24h continuous recording / 45-day standby | 100 hours active recording | 32h Continuous Opus Streaming |
📚 Related Engineering Teardowns & Reviews
Browse All 158 Articles →WHOOP MG (27.3g On-Demand ECG, Blood Pressure Insights & 14-Day AI) vs Muse S Athena ($475 41g 4-Ch EEG + 5-Optode fNIRS Brain Headband) vs Circular Ring 2 Comparison: Cardiovascular vs Cortical AI
A technical electrophysiological-ECG, cuff-calibrated blood-pressure, and cortical fNIRS+EEG comparison of the WHOOP MG ($359/yr Life tier, 27.3g IP68 screenless biometric strap with conductive-clasp single-lead ECG AFib screening, overnight Blood Pressure Insights, Healthspan AI, and 14+ day Wireless PowerPack battery), Muse S Athena ($474.99, 41g fabric headband combining 256Hz 4-channel EEG with 64Hz 5-optode fNIRS prefrontal oxygenation sensing), and Circular Ring 2 ($349).
Circular Ring 2 (3.0g Single-Lead ECG & FDA AFib AI) vs Amazfit Helio Ring ($199 3.65g Palmar EDA Stress & Watch Fusion) vs Oura Ring 4 Comparison: Cardiac ECG vs Sympathetic EDA
A technical electrophysiological-sensor, autonomic-stress, and subscription-model comparison of the Circular Ring 2 ($349, 3.0g 2.55mm titanium smart ring featuring on-demand single-lead ECG recording, FDA-cleared Atrial Fibrillation detection, 8-day battery, 30-min wireless charging, and $0/mo Kira AI), Amazfit Helio Ring ($199, 3.65g 2.6mm titanium ring with palmar Electrodermal Activity sweat-stress sensing, BioTracker PPG, 10ATM waterproofing, and $0/mo Zepp Watch+Ring data fusion), and Oura Ring 4 ($349).
Unitree B2 ($75k 60kg 360N·m, >40kg-Load, IP67 & 2,250Wh Industrial Quadruped) vs Hello Robot Stretch 3 ($24.95k 24.5kg Prismatic-Mast Dual-RealSense Open VLA Manipulator) vs Lynx M20 Comparison: Heavy Patrol vs Home VLA
A technical 360 N·m joint actuator, prismatic Cartesian mast vs serial arm kinematics, and IP67 field endurance comparison of the Unitree B2 ($75,000 tier, 60kg IP67 industrial quadruped delivering 360 N·m peak joint torque, >6.0 m/s speed, >=120kg standing / >40kg continuous walking load, and >5h / >20km range on a 2,250Wh battery), Hello Robot Stretch 3 ($24,950, 24.5kg 33×34cm mobile manipulator with 1.1m lift mast, 52cm telescoping arm, Dex Wrist 3, head D435i + wrist D405 RGB-D, Intel NUC12, and 100% open-source ROS 2 / LeRobot VLA stack), and DEEP Robotics Lynx M20 ($18,900).
Qualcomm RB3 Gen 2 Vision Kit ($399 QCS6490 12-TOPS Hexagon NPU & IMX577/OV9282 Dual-Cam) vs Khadas Edge2 Pro ($239 25g 5.7mm RK3588S2 6-TOPS 16GB SBC) vs RUBIK Pi 3 Comparison: Calibrated VIO vs Ultra-Thin SBC
A technical 6nm Hexagon 770 Tensor NPU vs 8nm RK3588S2 NPU, factory-calibrated VIO/SLAM camera mezzanine vs 5.7mm FPC density, and Linux toolchain comparison of the Qualcomm Dragonwing RB3 Gen 2 Vision Development Kit ($399, ~200g QCS6490 8-core Kryo 670 + 12-TOPS NPU + Triple ISP kit bundling a 12MP IMX577 + global-shutter OV9282 Vision Mezzanine, Wi-Fi 6E, and Qualcomm Linux / ROS 2 / AI Hub), Khadas Edge2 Pro ($239, 25g 82×57.5×5.7mm credit-card SBC with RK3588S2 6-TOPS NPU, 16GB LPDDR4X, 64GB eMMC, 3× CSI, 4× displays, and OOWOW), and Thundercomm RUBIK Pi 3 ($119).
