What is an 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.
FNSKUs help identify the seller of a product, and ASINs identify a unique product.
No, because Amazon FBM sellers don’t send their products to an Amazon warehouse, they do not need FNSKUs.
If you plan on using Amazon FBA (Fulfilled by Amazon) then yes they are required.