Used to test the consistency of concrete using the penetration of a half sphere into plastic concrete. A 1″ (2.5-centimeter) penetration by the kelly ball corresponds to about 2″ (5 cm) of slump. The apparatus consists of 30 lb. (14kg) cylinder with hemispherically shaped bottom and handle. Stirrup or frame guides handle act as reference for measuring the depth of penetration. The stirrup handle is graduated in 0.25″ (6.4mm) increments on one side and half-centimeter increments on the other side for measureing the depth of penetration. Concrete may be tested as it is placed into forms prior to any manipulation or in a suitable container.