These are four puzzle rings
, all novel designs by Bram Cohen. The object is to scramble the rings and then bring them back to the ring shape. Very difficult!
The rings on the photos are made of alumide, which is as strong as nylon, but gives the puzzle a metalic look.
You can also buy these rings separately:
Se also Ring set 1
Note that while looking good, the alumide is more stiff and brittle than the recommended "white, strong & flexible" material.