cun distance unit
One cun = width of the thumb, in the middle, at the crease. or. One cun = the distance between the distal and proximal inter-phalangeal joints of the 3rd (middle) finger. One and 1/2 cun (1.5) = width of the two forefingers. Three cun = combined breadth of the four fingers, at the level of the pinky finger's first joint above the palm of the hand.