The diameter of an official volleyball measures from 8.15 to 8.39 inches, and the circumference is 25.5 to 26.5 inches. These measurements remain constant among balls used in men's and women's competition.
Volleyballs are typically constructed from genuine or synthetic leather. Most balls used today consist of 18 nearly rectangular panels arranged in six identical sections of three panels each. Indoor volleyballs may be white or a combination of two or three distinguishable colors, while outdoor "beach" volleyballs tend to be solid white or brightly colored and bear a rougher outer texture. The internal air pressure of the ball may be adjusted through the air valve and should be from 4 to 5 pounds per square inch.