A reusable box, which we take with us to the supermarket to store bulk groceries in. That type of box, which we use again and again needs to be thick and rigid to be washable and reusable. So the downgauging part of “reduce” is not the right approach. Also for recycling facilities, downgauging is a problem.
In Germany, there is an increasing number of unpacked stores (Unverpackt). For some products, that makes absolute sense. But it may lead to food getting wasted, because unpacked bulk food naturally tends to have a shorter life cycle, tends to break easier.