Largest hailstone ever recorded is the size of a volleyball

"Even after melting, the stone [produced from the thunderstorm that struck Vivian, South Dakota, U.S. of A., on 23 July 2010] still measured 8.0 inches in diameter and weighed nearly 2 pounds (1 pound, 15 ounces) with a circumference of 18.62 inches"


Via Digg. NOAA article here: http://www.noaa.gov/features/02_monitoring/hailstone.html