A major soft drink manufacturer decided that providing choices in the container size in the six-packs of its beverages might help move the product off the shelves. The unique selling idea was to have several different container sizes in the very same six-pack. One of the most successful packages comprised two 250 ml bottles, two 500 ml bottles, and two 1000 ml bottles. To the bottler's surprise, after purchasing the beverage, most people chose to drink from the 1000 ml container first. Post-marketing research showed why: It was the litre of the pack.