Carry-on Baggage - China Southern Airlines

What the official page says

The maximum accepted weight of free carry-on baggage per passenger is 5 kg. Passengers holding a first class ticket may carry two pieces of free carry-on baggage; passengers holding a business class or economy class ticket can only carry one piece of baggage. For every carry-on baggage, its three dimensions must be no larger than 20x40x55cm. Carry-on items that exceed the limits to weight or volume should be transported as checked baggage.