Hollowcore planks (hollowcore floor units are referred to as planks, panels or slabs) are made via slip-forming or extrusion. Hollowcore derives its name from the empty internal cores that run the entire plank length, thereby reducing their weight. Hollowcore floor planks are precast, prestressed elements with the reinforcing placed around the cores. Planks are normally 1200 mm wide. A thin topping of reinforced concrete is often placed on-site to produce composite units and a level floor surface, but the planks can also be used with grouted joints only.