68 cm (27 ins) <= circumference <= 70 cm (28 ins)
68 - 70 inch circumference
It depends on how old you are and what age group you are in. Anyone under U-8 uses a size 3 ball. When you get to U-9 you start to use a size 4. In middle school soccer you use a size 5 ball.
A strike ball has less padding and is used for training and a match ball is used for games and has more padding and better flight in the air.
5 to 6 lbs...not too hard...just right..