The Garmin DriveSmart 66 MT-D is compatible with the Garmin BC 50 reversing camera. The BC 50 has been specially developed for compatible Garmin navigation devices such as the DriveSmart series. You can therefore connect the BC 50 to your Garmin DriveSmart 66 MT-D. The BC 40 is not explicitly mentioned in the compatibility lists, so compatibility with this camera is not guaranteed.