Word for singular boardgame or boardgame expansion, but not both

I'm writing an auction site specifically for selling board games, and I'm a big believer in ubiquitous language and that the right naming makes the code design stronger. This is why it is paining me so much that I'm struggling to think of a term for the abstract of an item in a lot.

An auction will have many lots. A lot will have one or many items. An item could be a boardgame or a boardgame expansion. When adding an item a user will look up from a list of boardgames and boardgame expansions. What is that a list of? At the moment I'm using the BGG term "thing" and I hate it.

The best alternatives I have are product and box. Both of which are improvements, but both vaguer than I'd like.

Edit: Trying to add a better example. If I wanted to group things that could be cars or pick-up trucks, but not carrots, I could use the word vehicle.

SKU or Stock Keeping Unit is the business/stock control term for each distinct item offered for sale. It can refer either to the item itself or a unique identifying number/code (which in modern retail often corresponds to a unique bar code). Commonly each separate item would be (and have) a separate SKU if it was sold separately: so a board game would be a SKU, and expansion pack 1 would be a different SKU, and expansion pack 2 different again. Of course it's not specific to board games and expansion packs. See also Shopify's explanation.