Take SF as an example. SF Express is land transportation. SF has standard express and SF special price. The standard express delivery is usually by air, and the special price is by land. SF Express means SF Express, which usually takes two days to arrive. SF Express is the aviation part. One kilogram is the first weight in 23 yuan, and the second weight is 15 yuan. SF Express is the land transportation part, the first weight 18 yuan and the second weight 12 yuan will arrive in two to three days. The difference between SF Express and Standard Express is the mode of transportation, and SF Express is another mode of transportation introduced by SF Express. The land transportation used by SF is completely different from SF, and SF takes air transportation. The speed and price of the two are completely different.