From what I've seen here though, you can't share a product attribute between products.
So, if I had 100KG of sand stock, and three products: 1kg of sand , 5kg of sand , and 20kg of sand . I can't seen how to have each of those products draw from the same pile of stock - even with product attributes. It could be I'm missing something here, but I spent quite a while looking at it last year.
My understanding of attributes is that you might have 4 red in stock, 7 blue in stock and 0 yellow in stock. But the quantity in stock are unique per product. I could be wrong though
Maybe there is a confusion between association to a grouped product (a simple product can only be associated to one grouped product) and to attribute values where a a product can be associated to several attribute values of different attributes.
My example for you is:
- Your product is "Sand" (Manage inventory method: Track inventory by product attributes)
- Your attribute is Weight Options, type Drop Down List whose values are 1 kg., 5 kg., 20 kg. and all of them associated to a simple product (named "1 kg of sand", non visible individually, whose inventory is 100), with product quantities of 1, 5, and 20 respectively.
Please let me know if it works