Size is as-packaged, or the diameter of loose marbles. ("D" is the diameter of round items other than marbles.)
Helter Skelter features a multi-color double ribbon core spiraling around each other from one end of the marble to the other. Color schemes include a blue/yellow ribbon twisting around a yellow/pink ribbon, white/purple twisting around white/orange or blue/purple ribbons - our choice of color please. This is a larger shooter sized marble measuring 7/8 to 1" or 22-25mm.