add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );
function your_prefix_register_meta_boxes( $meta_boxes ) {
	$meta_boxes[] = array (
		'title' => 'Car Rental',
		'id' => 'car-rental',
		'post_types' => array(
			0 => 'car-rental',
		),
		'context' => 'normal',
		'priority' => 'high',
		'fields' => array(
			array (
				'id' => 'price',
				'type' => 'number',
				'name' => 'Rental price',
				'required' => 1,
				'prepend' => '$',
			),
			array (
				'id' => 'car_year',
				'type' => 'number',
				'name' => 'Car Year',
				'required' => 1,
			),
			array (
				'id' => 'max_passengers',
				'type' => 'number',
				'name' => 'Max passengers',
				'required' => 1,
			),
			array (
				'id' => 'fuel',
				'name' => 'Fuel',
				'type' => 'select',
				'placeholder' => 'Select an Item',
				'options' => array(
					'Gasoline' => 'Gasoline',
					'Petrol' => 'Petrol',
					'Electricity' => 'Electricity',
				),
				'required' => 1,
			),
			array (
				'id' => 'door',
				'name' => 'Door',
				'type' => 'select',
				'placeholder' => 'Select an Item',
				'options' => array(
					2 => '2',
					4 => '4',
					5 => '5',
				),
				'required' => 1,
			),
			array (
				'id' => 'gearbox',
				'name' => 'Gearbox',
				'type' => 'select',
				'placeholder' => 'Select an Item',
				'options' => array(
					'Tiptronic' => 'Tiptronic',
					'Manuatic' => 'Manuatic',
				),
				'required' => 1,
			),
			array (
				'id' => 'fuel_usage',
				'type' => 'text',
				'name' => 'Fuel Usage',
				'desc' => 'Ex: 101/100km',
			),
			array (
				'id' => 'engine_capacity',
				'type' => 'text',
				'name' => 'Engine capacity',
				'desc' => 'Ex: 2500 cc',
			),
			array (
				'id' => 'max_luggage',
				'type' => 'text',
				'name' => 'Max luggage',
			),
			array (
				'id' => 'mileage',
				'type' => 'text',
				'name' => 'Mileage',
				'desc' => 'Ex: 500km or Unlimited',
			),
		),
	);
	return $meta_boxes;
}

add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes_2' );
function your_prefix_register_meta_boxes_2( $meta_boxes ) {
	$meta_boxes[] = array (
		'title' => 'Car rental - Side',
		'id' => 'car-rental-side',
		'post_types' => array(
			0 => 'car-rental',
		),
		'context' => 'side',
		'priority' => 'low',
		'fields' => array(
			array (
				'id' => 'car_gallery',
				'type' => 'image_advanced',
				'name' => 'Car gallery',
				'force_delete' => 1,
				'max_file_uploads' => 7,
				'image_size' => 'post-thumbnail',
				'max_status' => true,
			),
		),
	);
	return $meta_boxes;
}