Made by Clever Toys, purchased 2007.
(wood, 5 inches by 7/8 inches thick)
Two rings each capable of holding 18 balls, with a central portion that moves 4 balls between the rings (there are a total of 32 balls);
there a total of seven pairs of balls that are joined.
The central portion has thick bars on each side constructed in a way so that when one ring is complete and can rotate,
the other ring cannot move
(and its balls cannot fall out).
The balls are arranged in an alternating pattern of single ball and joined balls, and because the bar can only contain one pair at a time
(because two pairs separated by a single ball would be 5 long),
this alternating pattern is always maintained as the puzzle is mixed up.
The goal is to mix it up and then restore the pattern shown above
(yellow at one end, light brown in the vertical sections, and dark brown at the other end).
presents a solution.