In reference to any single item offered for purchase, should I say 'sale item' or 'sales item' ?

Experience tells me it should be 'sale item', because 'sales' seems to be preferred in English for things involving, at least potentially, an arbitrary number of individual sales, which is not usually the case with a single item.

EDIT: And if it's not a single item I'm referring to, but rather a 'model' of individual items, thus an abstract collection of potential things, is it correct to say 'sales item' then? For example, as in 'The shops's sales items encompass the freshly released processor (model) CPX'.