Most commonly , they are about 1\/2 inch to 1 inch ( 1.3 to 2.54 cm ) in diameter , but they may range from less than 1\/30 inch ( 0.111 cm ) to over 3 inches ( 7.75 cm ) , while some art glass marbles for display purposes are over 12 inches ( 30 cm ) wide .
Usually they are about 1\/2 inch to 1 inch ( 1.3 to 2.6 cm ) in diameter , but they may range from less than 1\/30 inch ( 0.111 cm ) to over 3 inches ( 7.75 cm ) .