参考一下这个吧：
WCO/UN Comtrade Supplementary Quantity Units
In addition to  net weight, all detailed Comtrade data also have supplementary quantity units.  These units of measurement are based on the standards of quantity recommended by the World Customs Organization (WCO):

UN Comtrade Code        WCO Abbreviation        Description
1        -        No quantity
2        m2        Area in square meters
3        1000 kWh        Electrical energy in thousands of kilowatt-hours
4        m        Length in meters
5        u        Number of items
6        2u        Number of pairs
7        l        Volume in liters
8        kg        Weight in kilograms
9        1000u        Thousand of items
10        U (jeu/pack)        Number of packages
11        12u        Dozen of items
12        m3        Volume in cubic meters
13        carat        Weight in carats

http://unstats.un.org/unsd/trade ... de-Reference-Tables