4iiii

Shimano GRX RX810/RX820 PRECISION 3+ Left-Side Power Meter

What Our Gearhead® Experts Are Saying:

"I’ve installed this on a GRX build for gravel training, and setup was straightforward. It paired with my head unit almost instantly and the data has been consistently accurate. The battery life is impressive, and having Find My built in adds real peace of mind when traveling with the bike."

Big gravel miles and structured training blocks demand more than guesswork. The GRX RX810/RX820 PRECISION 3+ Left-Side Power Meter from 4iiii gives us reliable, actionable data every time we roll out, whether we’re chasing a new FTP or building steady endurance for long mixed-terrain days.

This Ride Ready unit arrives pre-installed on a brand-new Shimano GRX left crank arm, making installation as simple as swapping your existing non-drive crank. With +/-1% accuracy, automatic terrain selection, and cadence measurement, it delivers consistent performance insights across rough gravel, pavement, and high-cadence efforts. ANT+ and Bluetooth Smart compatibility connect seamlessly to most head units and training apps, while up to 800 hours of battery life from a CR2032 coin cell keeps maintenance minimal. Apple Find My integration adds an extra layer of security, helping us locate our bike when it’s not in use.