# How to figure out which .hex file to use

The name of a product is **not** enough information to find the right .hex
file.  Ask the light what firmware it needs!

1. Use the Version Check function (15 or more clicks from Off) to find out
   which flavor of the firmware the light has installed.  
   **WRITE THIS DOWN.**

2. Look up the model number in the [MODELS file](../MODELS),
   to get the name and MCU type.

3. Find (or build) the newest firmware for that model.  
   https://github.com/ToyKeeper/anduril/releases

The Version Check format has changed a few times.  Use
[this section of the manual](anduril-manual.md#Version_Check_Formats)
to learn about those formats and how to use them.  In most cases, it should
have a model number and a date... and you need the model number to find the
correct .hex file.