FAQs What is FNSKU? FNSKU stands for Fulfillment Network Stock Keeping Unit. It is used by Amazon so they can identify a product as being unique to a specific seller. What Is the Difference Between FNSKU and ASIN? FNSKUs help identify the seller of a product, and ASINs identify a unique product. Do Amazon FBM Sellers Need FNSKUs? No, because Amazon FBM sellers don’t send their products to an Amazon warehouse, they do not need FNSKUs. Are FNSKU Barcodes Required? If you plan on using Amazon FBA (Fulfilled by Amazon) then yes they are required.