Cardboard inserts do three jobs at once: they stop the product moving, they separate items so they cannot knock together, and they present the contents in a deliberate arrangement when the box opens. Because they are the same material as the box, the whole pack goes into one recycling stream — increasingly a hard requirement rather than a nice-to-have.

They are also the cheapest insert type to tool and iterate. A die is inexpensive relative to a foam or thermoform mould, so revising a fit after the first sample is quick and low-risk. For most non-fragile products this is where to start, and only move to foam or pulp if drop testing says you have to.