diff --git a/README.md b/README.md
index 23dd3f1..a322f4c 100644
--- a/README.md
+++ b/README.md
@@ -65,6 +65,7 @@ To get started with CAN Commander, follow these steps:
 ## Hardware Requirements
 - Microcontroller (Arduino Uno, Mega, Nano, Pico, ESP8266, ESP32)
 - MCP2515 (Make sure you verify the crystal 8/16/etc)
+- only for 3.3V microcontrollers: a 4 channel 3.3-5V bi-directional level shifter 
 
 ![20240113_010817](https://github.com/MatthewKuKanich/CAN_Commander/assets/113921492/410fce00-e54a-4fb6-ad24-4d3d278d5a5b)