This is a great answer to the needing different names for the same stock, but picture the invoice you   created as an example but instead of two what if I sold 50 oil filters. The invoice would have 50 lines all of oil filters. I also might sell 40 of another item, (identical but with different sku) so that would make my invoice 90 lines long. I can't send that to a customer's accounting department when it should be two lines, one for each item and then the quantity as 50 and 40 respectively