X4 Stellar 2025

Pocket High Performance

Exceptional performance designed specifically for everyday carry. We have meticulously crafted this flashlight to feature a stylish look, rugged durability, and comfortable touch, delivering outstanding feel as well as performance.

Interchangeable optical components, removable tail magnet, and attachable accessories allow you to customize the flashlight to suit your individual needs. Paired with the high-performance Lume X1 boost driver, the X4 delivers class-leading efficiency, maintaining consistent brightness and extended runtime. This is our vision of a high-performance EDC flashlight.

In 2025, we further refined the design for enhanced durability, implemented a stronger magnet, and introduced an all-new wood grain green body color.

Raised Switch Bezel

Data Sheet

Features

• Compact Size - 107mm x 32mm x 25.5mm 
• Weight -  95gram ; 
• Quad 3535 LED Emitter Configuration
• Battery - unprotected flat-top 21700 cells only (not included, recommended to use high-drain cells including Molicel P42, P45, P50, or Samsung 40T, 50S, or Vapcell T50)
• RGB Auxiliary (front), Illuminated Side Switch with Charging Indicator
• CNC Construction, SS Glass Bezel and Switch bezel,  6063 Aluminum alloy body
  
• Optics - 30-deg Beaded TIR (default),  15-deg Beaded also included
• Open-Source Anduril2 User Interface / Firmware
• Lume X1 40W Boost Driver, Constant Current Regulated (up to 95% efficiency) with UDR (Ultra Dynamic Range)
• Automatic Thermal Regulation, Low Voltage Cut-off, Reverse Polarity Protection
• Improved Be-Cu Silver-Plated Springs
• Toughened Front Glass Lens, AR Coated (~98% transmittance) 
• 10W Fast Charging, Firefly Patented Magnetic Type-C Port (Patent 2023235776065)
  
• Stronge magnetic Tail Cap (user-removable) (Patent Pending）
  
• Optional Firefly detachable Lantern Kit (Patent Pending）
• Water Resistance - IPX8
• Drop Resistance - 2m

Included Accessories 

• 1x New Design Two-way SS Clip
• 1x SS Lanyard ring
• 1x Lanyard
• 1x Tail Magnet
• 1x 15-deg Beaded TIR Optic
  
• Spare O-rings

Stellar X4 is compatible with a variety of optional accessories including a lantern kit and lampshades, which can be attached to the front bezel thread. 

User Interface: (Anduril V2)

This flashlight uses the open-sourced Anduril user interface. Anduril 2 is an open-sourced software and distributed under the terms of GPLv3. The source can be accessed here. 

By default, this flashlight begins in Simple UI with 5 brightness levels. Enter the hidden Advanced UI to access additional features and more configuration options.

Details can be found in Anduril User Guide. 

Charging

Stellar X4 features an intelligent 10W battery charger. For optimal charging, use a USB-C port that can source 5V 3A. Upon the start of charging, the side-switch illuminates red. When charging is complete, the red indicator turns off. A flashing red indicator indicates a charge fault (e.g. battery not inserted). 

For battery safety, cells below 3V are pre-charged at 100mA before the full 10W charge starts, transitioning to constant voltage, and ending with trickle-charging. The charger includes a 10-hour safety timer to prevent extended charging.

While not recommended, the flashlight may be used while charging, but if operated at higher power levels than the charging rate, the battery will not be charged. 

Note - If a charge fault (flashing red LED on the side switch) occurs towards the end of charge, please remove the flashlight from the charger and contact Fireflies. 

Battery Level Indicator

Anduril2 UI uses the front RGB auxiliary LEDs to indicate the current battery level upon turn-off. The colors correspond as follows:

This post-off display can be turned off or configured in Anduril. 

Operation Notes

• Stellar X4 is a high-performance flashlight capable of up to 40W and generates a lot of heat. Please understand that this is not a toy and should be handled with safety.
• The default thermal regulated limit is set at 50C. This can be configured by the user to be higher or lower via the Anduril user interface.
• To prevent accidental activation of the flashlight, it is recommended to lock-out the flashlight (4 clicks from off to lock or unlock) before storage, or unscrew the body slightly as a mechanical lock-out. 
• Stellar X4 has low-voltage protection which cuts off power at 2.8V. It is recommended to begin recharging the cell before this happens to increase battery longevity. 
• For advanced users, the Lume X1 driver features UPDI flashing pads for advanced users to perform their own firmware updates or to flash custom firmware binaries.