Gentex K21 Auto-Dimming Rear View Mirror w/Compass and Temp(select your vehicle for custom pricing)  will improve and personalize your vehicle. Equinox Auto-Dimming Rear View Mirrors by Gentex - selected by many auto enthusiasts in the top automotive discussion forums. Gentex K21 Auto-Dimming Rear View Mirror w/Compass and Temp will deliver the results you are looking for! The K21 Auto-Dimming Rear View Mirror detects dangerous rear-approaching light and eliminates it with “intelligent” circuitry. What’s more, less glare means less eyestrain and driver fatigue.