Sistema Ring (Terrestrial Surfaced, 3 Green Garnets)Sistema Ring (Terrestrial Surfaced, 3 Green Garnets, 17mm, MA+GGAR) from Parts of Four. Sistema series The Sistema series is first family within Parts of Four. As a mode of creation it expresses the core principle of P 4 which is modularity. The "body" and "insert" are separate parts joined together with pins. This leaves endless possibilities for iteration of material and form combinations. Natural Variation This item is made with a naturally