The apparatus is used to determine the workability of Portland cement & concrete. The Kelly ball test is considered to be simple and much faster than the slump test. Twice the Kelly ball reading approximately equals the slump. It consists of a cylinder with a ball shaped bottom and handle, together weighing 15 kg. A strip frame, guides the handle and serves as a reference for measuring the depth of penetration. The handle is graduated in mm. Penetration can be recorded to the nearest 0.5 mm.