diff --git a/latest/Firmware/Transponder/Binaries/README.md b/latest/Firmware/Transponder/Binaries/README.md
index e976c65..9d81c43 100644
--- a/latest/Firmware/Transponder/Binaries/README.md
+++ b/latest/Firmware/Transponder/Binaries/README.md
@@ -3,7 +3,20 @@
 This directory contains binaries for boards 11.3 and newer *purchased through the OpenMarine store*. If you do not use OpenPlotter 
 or you are unsure whether these apply to your board, please start a ticket or a discussion.
 
-### FW 4.1.0
+### How to select the right firmware
+
+Launch the MAIANA app and connect to the transponder. You may need to disable / disconnect MAIANA from Signal K first.
+
+- Your board's hardware revision (example: 11.6.0)
+- Your board's MCU model (example: STM32L422)
+- Your board's firmware revision (example: 4.0.0)
+
+Locate the appropriate binary in this directory. Ignore the last digit of your board's revision -- it doesn't matter. So if you have board 11.3.0 with an STM32L422 processor, the right binary is maiana-stm32l422-hw11.3-fwXXX.bin where XXX is the latest revision you see here. If you already have this firmware on your board, there is no update.
+
+
+## Firmware update history
+
+### Version 4.1.0
 
 This firmware release corrects the tuning of the crystal oscillator for the Si4467 chips. This applies to boards made after November 2021 which contain the following
 crystal:
@@ -12,3 +25,6 @@ crystal:
 
 The tuning changed by 5 KHz when the design had to migrate to this crystal due to supply problems. See issue [#103](https://github.com/peterantypas/maiana/issues/103)
 
+### Version 4.0.0
+
+This firmware release makes use of the new MAIANA bootloader.