The Hover Pack is a power-up that only Bentley can use. It allows Bentley to either gain height, travel large distances, or both.
The hover pack serves different purposes in Sly 2: Band of Thieves, verses Sly 3: Honor Among Thieves and Sly Cooper: Thieves in Time, due to his being confined to a wheelchair. In Sly 2, the hover pack drains the Gadget Meter by a small amount but its usage is limited to approximately four seconds per use. It is used primarily to gain height, but can be used to travel a large distance.
In Sly 3, the hover pack gives Bentley's Wheelchair the ability to triple jump, and has unlimited usage, until the wheelchair touches the ground. The hover pack is automatically assigned to and cannot be assigned to any other button.
In Sly Cooper: Thieves in Time Bentley has the hover pack at the beginning of the game. It provides a small height boost and allows Bentley to float a longer distance laterally than with a single jump. It consumes the Gadget Meter, which then refills quickly after Bentley stops hovering.