Tungsten Carbide Balls - 3/8" inch (9.60mm) - 7 grams per ball High Density: 14.8 g/cc vs 11.3 g/cc for lead, 8 g/cc for steel High Hardness: 9 on Mohs Scale vs. 1.5 for lead, 4.5 for steel (diamond is 10) Magnetically recoverable (8 % Cobalt by weight) High density without toxicity of lead Not susceptible to corrosion