A robotic object handling system and robotic load handling device for operation thereon is disclosed. The object handling system includes a number of robotic load handling devices operational on a grid-like structure, the structure having sets of parallel tracks, disposed above a hive of stacked bins. The bins contain inventory items to be picked by the system. Load handling devices capable of carrying multiple bins of a single grid-spacing size or single bins of a multiple grid spacings are operational on the grid and retrieve and transport bins under the control of a computerised order picking utility.