MHD Activation Code (or License Key) is a unique alphanumeric string used to unlock tuning capabilities within the MHD Flasher app for BMW and Toyota Supra (A90) vehicles. Unlike traditional handheld tuners, MHD is a mobile platform where licenses are permanently tied to a specific Google/Apple account and the vehicle's VIN (Vehicle Identification Number) Key License Types MHD Tuning User Guide and Overview | PDF | Ios - Scribd