Shenzhen’s developed logistics industry provides an important guarantee for the city’s development. The size of Shenzhen’s logistics industry ranks second in the nation. Shenzhen has become one of the first batch of 22 national green freight distribution demonstration project cities. Three key logistics companies such as SF Express have entered China's top 500, and four logistics companies such as YH Global have been listed as "unicorns." Over 80% of China's supply chain management companies’ headquarters are in Shenzhen. Over 60 famous international logistics companies have established themselves in Shenzhen, including America's UPS, Germany's LTLS, Denmark's Maersk Group, and Cainiao Network Technology. The cities' primary logistics industrial zones/parks include Qianhai Bay Logistics Park, the Yantian Logistics Park, the Aviation Logistics Park, the Pinghu Logistics Park, and the Longhua Logistics Park. Some of the better known Shenzhen-based logistics enterprises include S.F. Express, Eternal Asia, and China South City.