TechnologyInside the core
Engineeredto disappear.
Nine sensors, a processor and ten days of power inside 24 grams. Everything that matters to the measurement, nothing that pulls your attention.
- Green, red and infrared emitters
- 7LEDs
- Peak optical sampling rate
- 256Hz
- Skin temperature resolution
- 0.01°C
- Core thickness, titanium shell
- 8.6mm
01Sensor array
Nine sensors. One window.
Sensor core · underside
Inside the core
Green LEDs
4 emitters · 25 to 256 Hz
Green light is absorbed by blood, so every heartbeat shows up as a tiny dip in the light that returns. Four emitters around the window keep the signal steady when the band shifts.
- Heart rate
- HRV
- Zones
02Signal processing
From noise to a heartbeat.
- 01CaptureLight and motion sampled up to 256 times a second, in sync.
- 02CleanArm swing, footstrike and ambient light subtracted on the band.
- 03DetectEvery beat timed to the millisecond, every interval stored.
- 04InterpretHeart rate, HRV, sleep and load scored against your own baseline.
Optical signal · 3.2 seconds of a tempo run
Raw light
What the photodiodes see mid-run. Arm swing moves the band and the blood beneath it, and that motion is far louder than your pulse.
- Signal quality
- 38%
- Heart rate
- 172 bpm
- A naive reading locks onto your cadence
03Validation
Measured against the reference.
Heart-rate error by activity
Mean absolute error in bpm against chest-strap ECG. Lower is better.
1.8 bpm
Mean heart-rate error against chest-strap ECG
0.97
Correlation of overnight HRV with ECG
±0.1 °C
Skin temperature against a clinical probe
81%
Four-stage sleep agreement with lab polysomnography
PACE Labs validation study, 2026. 212 participants aged 19 to 71 across all six Fitzpatrick skin types and 40 activity types. Accuracy depends on fit: wear the core snug, one finger above the wrist bone.
04Construction
Six layers. 8.6 millimetres.
- Sensor core
- 11 g
- Water resistance
- 10 ATM
- Titanium shell
- Grade 5
- Sensor window
- Sapphire
Emitters and receivers separated by black light barriers, so light only reaches a photodiode after travelling through skin.
05Power
Ten days. Your way.
The band also stores 14 days of full-resolution data, so nothing is lost if your phone is away for a training camp.
Where the power goes · 10.0% a day
- Optical heart rate34%
- Processing17%
- Bluetooth sync13%
- Motion9%
- Temperature4%
- GPS21%
- Haptic zone coaching3%
Estimated battery life
10.0days
Each cell is one day
- Fast charge
- 0 to 80% in 35 min
- Continuous GPS
- Up to 24 hours
06Data and privacy
Your body. Your data.
Processed on the band
Heart rate, HRV and sleep staging run on the core itself. Raw signals never need to leave your wrist.
Encrypted end to end
Data is encrypted on the band before it syncs, and stays encrypted in the app and in your optional backup.
Never sold, never advertised
No ads, no data brokers, no selling insights to insurers or employers. Not now, not later.
Yours to take or delete
Export your full history as CSV or FIT whenever you like, or delete your account and every byte with it.
07Specifications
Every detail.
Design & materials
- Sensor core
- Grade 5 titanium, 50.0 × 25.4 × 8.6 mm
- Sensor window
- Domed sapphire crystal
- Strap
- Double-weave recycled nylon with an elastane core, 24 mm
- Clasp
- MagLock titanium magnetic clasp, 40 N hold
- Weight
- 24 g total, 11 g core
- Colorways
- Carbon Black, Signal Orange, Stone Titanium
Sensors
- Optical array
- 7 LEDs (4 green, 2 red, 1 infrared) and 4 photodiodes
- Sampling
- Adaptive, 25 to 256 Hz
- Skin temperature
- Digital sensor, 0.01 °C resolution
- Motion
- 6-axis inertial unit, accelerometer and gyroscope
- Altitude
- Barometric altimeter
- Positioning
- Dual-frequency GNSS, L1 + L5
Metrics
- Heart
- Heart rate 24/7, resting heart rate, HRV (rMSSD), zones
- Sleep
- Stages, score, consistency, smart haptic alarm
- Health
- Respiratory rate, blood oxygen, skin temperature deviation
- Readiness
- Daily recovery score with contributors
- Training
- Training load, load focus, VO2 max, recovery time
- Running
- Pace, distance, elevation, cadence, stride length
Power & connectivity
- Battery
- Up to 10 days typical, 24 h continuous GNSS
- Charging
- MagCharge slide-on puck, 0 to 80% in 35 min
- Storage
- 14 days of full-resolution data on the band
- Wireless
- Bluetooth 5.3 Low Energy
- Water
- 10 ATM, pool and open-water swim tracking
- Compatibility
- iOS 17 and Android 12 or later
08Questions
How it works.
During sleep, the optical array times every heartbeat to the millisecond. PACE calculates rMSSD, the variation between consecutive beats, across your deepest stretch of sleep, when motion and stress are lowest, and compares it with your own 30-day baseline.
No. Dual-frequency GNSS is built into the core, so runs and rides record full routes, pace and distance with your phone at home. Everything syncs the next time the app is open.
The band adjusts LED brightness and switches between four photodiode paths in real time to keep signal quality high. Validation included every Fitzpatrick skin type. Dense tattoo ink directly under the sensor can reduce optical accuracy, so wearing the band on the other wrist usually helps.
Heart rate, HRV and sleep staging are processed on the band itself. Data is encrypted before it leaves the band, stored encrypted in the app and backed up to your account only if you choose. You can export or permanently delete everything at any time.
Firmware updates install over Bluetooth while the band charges. Every update, including new metrics and activity types, is free for the life of the product.
$299 · No subscription. Every metric included.
Decode yourself.
Reservations are open with no payment today. We confirm by email before anything ships. First deliveries February 2027.
