diff --git a/Appendix-C:-QMK-Firmware-Programming.md b/Appendix-C:-QMK-Firmware-Programming.md
index 2209586..4a50869 100644
--- a/Appendix-C:-QMK-Firmware-Programming.md
+++ b/Appendix-C:-QMK-Firmware-Programming.md
@@ -26,6 +26,14 @@ Whenever you see that, use the following syntax:
 
 and you'll be fine.
 
+## Choose the correct firmware
+
+Look for some writing on the base PCB (it sits flat against the bottom of the case, and it holds the microcontroller and the sensor optic). If you see that it has a version of "R1.005" or higher, use the `rev1_005` firmware. If it's "R1.004" or lower, use the `rev1` firmware.
+
+**LEFTIES ONLY:**
+- If you're compiling from source, use the `rev1` version of the firmware. Make sure to change the `rev1/rules.mk` configuration file to have the line `BOOTLOADER=atmel-dfu` instead of `BOOTLOADER=caterina`.
+- If you don't want to be bothered with all that, a precompiled hex file is available for you [right here](https://github.com/ploopyco/classic-trackball-lefty/blob/master/firmware/ploopyco_trackball_rev1_leftie_via.hex). It comes with VIA already configured.
+
 ## Building the Ploopy Trackball firmware
 
 With your terminal window open and pointed at your QMK build environment, compile the firmware with the following command:
@@ -45,8 +53,8 @@ For more details on building QMK firmware in general, see the [QMK firmware guid
 Putting the Ploopy Trackball into bootloader mode is very easy.
 
 1. Unplug it from your computer.
-2. Hold the "forward" button. This is the button just to the right of the ball; it normally sits under your ring (fourth) finger.
-3. While holding the forward button, plug the Ploopy Trackball into your computer. If you're using QMK Toolbox, it should show up in the console. If using `dmesg`, it'll show up as an Atmel DFU device.
+2. If you're using a right-handed Ploopy Classic, hold the "forward" button. This is the button just to the right of the ball; it normally sits under your ring (fourth) finger. If you're using a left-handed Ploopy classic, hold the "back" button.
+3. While holding the button, plug the Ploopy Trackball into your computer. If you're using QMK Toolbox, it should show up in the console. If using `dmesg`, it'll show up as an Atmel DFU device.
 
 And that's it. While plugged in this way, the Ploopy Trackball will accept new firmware.