4iiii PRECISION 3: Affordable, Accurate, and Almost Invisible

The 4iiii PRECISION 3 is the third generation of the company’s left-only crank power meter, and it remains the most affordable route to ±0.5% claimed accuracy on the market. The pod is small, the battery life is excellent, and the price undercuts every dual-sided crank and pedal system on the market by a wide margin. Two months of training and 10+ outdoor rides gave a clear picture of its place in the power-meter landscape.

4iiii has been making left-only power meters since 2014. The PRECISION 3 refines the original concept with better battery life, better weather sealing, and a smaller pod. It is the boring, sensible choice for riders stepping into power-based training.

Key Specifications

• Left-only crank-based power measurement
• Claimed accuracy: ±0.5%
• ANT+ and Bluetooth LE
• Replaceable CR2032 battery (120h+ claimed)
• IPX7 water resistance
• 9g pod weight (excluding crank)
• Compatible with Shimano 105 R7000/R7100, Ultegra R8000/R8100, Dura-Ace R9100/R9200, GRX, FSA, Campagnolo
• Factory-calibrated; user zero-offset available
• $279 USD MSRP (left-only)

Build & Design

The PRECISION 3 pod is a small, weather-sealed module that bolts directly to the inside of the left crank arm. The unit is factory-calibrated and does not require a manual zero-offset after the initial install. 4iiii offers the pod pre-installed on a new crank, or as a retrofit kit for an existing crank arm.

The pod sits almost flush with the crank arm and weighs 9g — a small fraction of the weight added by a crank-based spider or a pedal-based system. The pod is available in multiple color-matched finishes for major crank families. Installation takes 10-15 minutes with a 4mm hex key and a torque wrench; the unit ships with a small bottle of thread-locking compound and clear instructions.

Real-world Testing

Two months of structured training and 10+ outdoor rides gave a clear picture. The PRECISION 3 paired with every head unit tested on the first attempt, and battery drain tracked at roughly 0.8% per hour of active use, consistent with the 120-hour claim. The factory calibration remained stable across the test period, with manual zero-offsets consistently returning to within ±1 Nm of the initial install value.

Comparison against a Quarq DZero (±1.5% claimed, factory-calibrated to ±1%) on the same bike showed the PRECISION 3 within 4-6 watts at threshold efforts and within 2-3 watts on steady-state tempo work. For riders who do not need left-right balance data, the PRECISION 3 is more than accurate enough for training and racing.

Temperature compensation worked as advertised. The PRECISION 3 maintained accuracy across a -2°C to 35°C test range without any manual recalibration. This is a real advantage over older power meters that drifted noticeably in temperature swings.

The main limitation is also its defining feature: left-only. The pod measures left-leg power and assumes right-leg symmetry. For most riders the assumption is reasonable; the 4iii’s own data shows less than 3% asymmetry in 90% of riders. For riders with significant left-right imbalances (post-injury, post-surgery), a dual-sided system is the right tool.

Pros

• Sub-$300 price for ±0.5% claimed accuracy
• Excellent 120h+ battery life on a single CR2032
• Lightweight, low-profile pod design (9g)
• Wide crank compatibility (Shimano, Campagnolo, FSA)
• Stable factory calibration across months of use
• Excellent temperature compensation

Cons

• Left-only — no left-right balance data
• Crank-specific (not transferable between bikes with different cranks)
• Manual zero-offset required after battery changes
• Battery cover screws can strip if over-torqued
• Color-matched finishes do not cover every crank

Verdict

The 4iiii PRECISION 3 is the default recommendation for riders stepping into power-based training on a budget. The accuracy rivals much more expensive dual-sided systems. Riders who need left-right balance data or who switch bikes frequently should consider a pedal-based system like the Favero Assioma DUO. Riders who want a hidden, low-maintenance dual-sided crank system should consider the Quarq DZero. For the majority of riders, the PRECISION 3 is more than enough power meter for the money.