Tekonsha Primus IQ Brake Control for GM Vehicles (2003 and up) Includes universal wiring harness to connect brake controller to vehicle tow package. No level adjustment necessary - it adjusts itself to varying terrain as you drive. Digital display depicts voltage delivery to trailer during braking. Continual diagnostics check for proper connection and shorted magnet. "Boost" feature gives the ability to apply more initial trailer braking power.