I Have Seen NAICS Codes with More than 6 Digits. What are These?

Industries in the United States are identified by a six-digit code. Each manufacturing and mining product or service is identified by a ten-digit product code. The product coding structure represents an extension, by the U.S. Bureau of the Census, of the six-digit industry classification of the manufacturing and mining sectors. The product classification system operates so that the industrial coverage is progressively narrower with the successive addition of digits.