Well, the onliest thing I could find on the official Major League Baseball site ( http://mlb.mlb.com/NASApp/mlb/mlb/official_info/official_rules/objectives_1.jsp ) wuz "It shall weigh not less than five nor more than 5 1/4 ounces avoirdupois and measure not less than nine nor more than 9 1/4 inches in circumference." By slicing the pie into a square, the so called 'diamond' are nothing but a 90 foot square, I line derive that the ball be between 2.866 and 2.956 inches in diameter. I say that .004 inches between 2.956 and 3.000 is too close to call, especially since the game is played on that diamond and not a diameter. Avoir Dupois was a shortstop on the old Albuquerque Dukes, he never made it to the Bigs as he was just a light weight, the French never having comprehended baseball. He was such a lightweight that when he slud into third he would float into the air, voila! The Little League ball is the same size as the Big League ball, even tho the players are smaller and they use metal bats. The diameter of the sand lot ball depends on how many layers of electricians tape is required to hold it together. This is not the origin of the phrase 'black ball.' We usually wore the cover rather than knocked the cover off the ball, none the less there was a ground rule that if a fielder managed to snag the ball out of the air by the end of the loose flapping tape, it was a strike and not an out unless it was the third strike. So any way the ball is way close to 3 inches in diameter, but the official rule uses circumference not diameter. Probably, along with the "not less than or more than" to allow for the bulge of the stitches.

According to United States Patent # 4256304, baseballs are allowed to be have a diameter of between two and seven-eighths inches and three inches. (Source: http://www.freepatentsonline.com/4256304.html). Note - oddly enough, I had a friend send me a picture of a hail-stone from Ft Worth, TX, that was slightly larger than a baseball in the same picture whichn is attached. I was trying to find how large the hailstone was. Hope this helped you.((http://kxas.weatherplus.com/weathernews/8371898/detail.html).