Certain types of bowling balls when places in water float Explain how this is possible?

Certain WEIGHTS of Bowling balls float.

Bowling balls have a volume of 6250 cm3. An equal amount of water would weigh 6.25 kilograms. A bowling ball that weighs less than 6.25 kilograms--8-pound, 10-pound and 12-pound balls--will float. 14-pound and 16-pound balls, having a density higher than 6.25 kilograms, will not float.