Replacement ZED 12 Black Heel Assembly. If you need hardware for a pair of bindings, then purchase a quantity of two.
G3 bindings are junk. Clever design but exceedingly poor quality and highly unreliable. Almost everyone I know who owns these bindings has had trouble: pins going missing on toe pieces, heel piece slippage, catastrophic brake failure, you name it. Many retail stores are no longer selling these bindings as a result. C’mon G3, you’re better than that!