A Backpack (バックパック, Bakkupakku?) is a support panel that appears in Kingdom Hearts 358/2 Days. It allows you to pick up two additional items in the field when equipped, from either Treasure Chests or enemy drops.
There are three Backpack panels that can be obtained, allowing you to carry up to six additional items when equipped normally. Backpack panels can be linked to a Pack Extender, doubling their effects.
The Pack Extender ④ (拡張パック④?) is a support panel that doubles the effect of each Backpack panel in its link zone. If all three Backpacks are linked to the Pack Extender, twelve additional items can be picked up.
Obtaining Pack Extender