Netweight and supplementary quantity unit are only available for 4 and 6 digit HS classification and 3,4, and 5 digit SITC classification. The reason is that netweight/quantity can be difficult to be interpreted at higher level. However, you can always aggregate netweight/quantity by yourself, if necessary.

I am wondering what the difference is between the net weight and the supplementary quantity. Is the net weight the primary unit declared by the member countries and is the supplementary quantity the secondary unit?  For example when I check the following trade flow I get this result: 1 Period Trade Flow Reporter ...