Radio group field

$metaBox->addField(array(
	'type' => 'RadioGroup', //string Type of field is RadioGroup
	'id' => 'car_brand', //string ID of the field as it will be later accessible by get_post_meta()
	'label' => 'What is your favorite car brand?', //string Label for the field
	'options' => $carBrands, //array of key => value pairs which will be Radio buttons
	'default' => $key //key, a value from the options array
));