A multitool that uses the empty space inside of the steerer tube. The tool mainly consists of two heat-treated steel hex wrenches that extend down from a rubber stem cap into the existing steerer tube. You just pull them out to use them. The wrenches have different bits at each end, allowing for choices between T25 torx, 4mm, 5mm or 6mm hexes – depending on which end of which wrench is used. [Source]