Thank you very much sir for replying me but actually I checked in the web of china southern and they mention some restriction of size and my checked luggage(which is in 30 inch size) is beyond the restriction, & also my ticket is for economy class that’s why I am asking you and one more thing that as you mentioned that they charged 1.5% of the total fare for above 20 kg in economy class, so I want to know the upper limit of kg, that means the maximum weight limit for which they can charge.