Heavy Duty Plastic Construction: For transportation of L-BOXX's and other materials;Rubber wrapped wheels and ball bearing casters: For smooth transport across finished surfaces;Integrated Click & Go System Locks: Allow any size L-BOXX to be clicked and stacked on the dolly;Compatible with: L-BOXX-1, L-BOXX-2, L-BOXX-3, L-BOXX-4, L-BOXX-3D and L-BOXX-1A