The HP Thunderbolt 3 Power Cable A (855116-001) is a power cable for HP’s Thunderbolt 3 docking setup. It is specified for use with the 150W HP docking station P5Q58AA#ABA.
The listing also names the HP Elite x2 1012 G1, HP EliteBook 840 G3 Notebook PC, HP EliteBook x360 1030 G2 and HP EliteBook Folio G1 Notebook PC as compatible models. This cable is a distinct part from other HP Thunderbolt 3 cable numbers, so its 855116-001 reference identifies the item.