Hoppers are upgradable to allow them to transfer items to chests within a certain radius of the hopper, move more items at once, or to pick up items in a larger area.
To upgrade a hopper, left click it with an empty hand.
10 Block Range for Chest Link
Moves 1 Item at a time
20 Block Range for Chest Link
Moves 2 Items at a time
+2 Suction
30 Block Range for Chest Link
Moves 3 Items at a time
+2 Suction