There are clearly 2 different sized circles here, the Yin Yang itself and the two smaller inner black and white circles.
These two smaller black and white circles are 1/3rd the size of the Yin Yang. The 2nd Phase is a bit more difficult to identify, though it is the spiraling arms of the white/black interface. If a figure 8 is drawn within the YinYang, we can create the 2nd phase's size.
