A regulation baseball is 9 inches around and weighs approximately 5 ounces. Many leagues use safety or "RIF" (reduced injury factor) baseballs, at least in T-ball and the lower "minor" leagues. Because safety baseballs are softer than regular youth baseballs, they don't hurt as much when they hit a player. A study by the Institute For Preventive Sports Medicine, headed by MomsTeam.com expert, Dr. David Janda, has shown that softer baseballs reduce the number and severity of head injuries, but another study by Dr. Janda shows that, contrary to the claims of some manufacturers, soft baseballs do not reduce the risk that a player struck in the chest by a ball will suffer commotio cordis, a potentially fatal cardiac injury. The use of soft baseballs will help players from developing a fear of the ball, which, once instilled, is difficult for a player to overcome.