FK Irons ONE Update

Engineered for consistency. Refined for precision.

The FK Irons ONE Update advances the simplicity and dependable power of the original ONE platform with critical performance and ergonomic upgrades. Designed, engineered, and manufactured in the USA, this accessible, wireless pen machine now delivers complete digital visibility and flexible power cell compatibility—keeping your focus entirely on the session.

Key Upgrades Over the Original ONE

✯ Digital LCD Display: Replaces the original color-spectrum LED with a crisp 1.1" screen showing real-time voltage, frequency (80–180 Hz), and battery life.

✯ 0.2V Fine-Tuned Stepping: Adjust voltage from 5.0V to 12.0V in precise 0.2V increments (compared to 0.5V jumps on the original).

✯ Dual-Battery Versatility: Ships with interchangeable short and extended caps to support standard 18500A cells or high-capacity 18650GA cells (3300 mAh) for up to 6.5+ hours of continuous runtime per charge.

✯ Enhanced Grip Compatibility: Re-profiled front collar ensures a seamless, flush seal with FK Irons disposable Ergo Shield grips.

Direct Comparison

Feature	Original FK Irons ONE	FK Irons ONE Update
Display Interface	Basic color-coded LED spectrum with minimal readout	1.1" Digital LCD screen showing voltage, hertz (80–180 Hz), and battery levels
Voltage Adjustment	Wider increments of 0.5 V	Fine-tuned increments of 0.2 V (5.0 V – 12.0 V range)
Battery Compatibility	Dual Panasonic 18500A cells only (approx. 2000 mAh each)	Dual-battery format: Supports both 18500A (short cap) and high-capacity 18650GA cells (long cap, 3300 mAh)
Max Runtime	~5 hours per cell (~10 hours total swap)	Up to 5.5 hours (18500A) / 6.5 hours (18650GA) per cell (~12 hours total)
Weight & Length	Fixed ~227 g; ~124 mm length	215 g / 126 mm (with 18500A) or 233 g / 134 mm (with 18650GA)
Grip System	Standard FK modular click grips	Standard modular grips + optimized integration for Ergo Shield disposable grips
Charger Included	Standard dual-bay USB dock	eFest Slim K2 dual-slot smart charger

This item includes free standard shipping within the contiguous United States.

Specifications

Stroke Options: 3.0 mm or 4.0 mm
Voltage Range: 5.0V – 12.0V (0.2V increments)
Operating Frequency: 80 Hz – 180 Hz
Dimensions:
      - with 18500A battery: 126 mm x 38 mm
      - with 18650GA battery: 134 mm x 38 mm
Weight:
      - with 18500A battery: 215 g (7.59 oz)
      - with 18650GA battery: 233 g (8.22 oz)
Needle Adjustment: Click-grip ratchet depth adjustment
Cartridge Compatibility: Standard universal membrane cartridges
Manual: FK Irons One Update

What’s in the Box

1x FK Irons ONE Update Machine
1x Standard Battery Cap (for 18500A)
1x Extended Battery Cap (for 18650GA)
2x Rechargeable Panasonic Batteries (18500A & 18650GA)
1x Dual-Slot Smart Battery Charger and cable
1x Custom Protective Travel Case
Spare O-Rings

* All sales are final for this item. Warranty service for this item provided directly by the manufacturer.