Cargo Hold
Prerequisite
The mech must have a transporter frame.
The mech’s body houses a small garage capable of storing a single creature, vehicle, or other object no larger than two size categories smaller than the mech. An operator can move from a stored vehicle to the mech’s cockpit as a move action, and vice versa. A mech can have no more than two cargo hold systems.
Source
Tech Revolution pg. 106