Sistema Bracelet v2 (Fuse, 9mm, DA18K)Sistema Bracelet v2 (Fuse, 9mm, DA18K) 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. DA18K: Dirty 18K Gold Skin. Dirty sterling silver (acid treated) with fused layer of 18K