Amazon are the worst for handling anything to do with co-mingled stock. I tried it with a few large products I got boxed from the brand, and customers were returning items with clear packaging from a company called Direct Vacuums who are a refurbisher. Amazon would not listen at all.

Basically, if you get any old crap and put it in a basic brown box with printed out barcode for the product on it (these can be made online), the FC will just stick it into co-mingled inventory. Doesent matter if its not manufacturer packaging, doesent matter if its non-genuine, the low paid staff at the FCs dont care, they get treat as bad as we do.

Then a customer buys the dodgy item and returns it, and you get lumbered with someone elses crap. DO NOT EVER USE COMINGLED INVENTORY.

As a side note too, if you use co-mingled stock on a listing with Amazon, they will use your stock to fulfill their orders - and as much as they recently reported to "treat Amazon retail and third party sellers equally" we all know this is a load of tosh. They steal the majority of sales on a lot of listings they are on and we all know this, some wont even sell alongside Amazon for this reason. At least if your own FNSKU is at an FC where the comingled stock has run out, you have at least a small chance your stock will be used, if Amazon works out the shipping to be cheaper for them.