When choosing the 'Hardware Color' -- either gold or silver, for the metal components on your collar(s), this selection pertains to the following standard supporting hardware components that come with the collar: the metal rivets that secure your collar hardware onto the fabric/webbing base, the round split ring (if it's a cat collar) // or D-ring (if it's dog collar) + the metal length adjuster + optional bell). These hardware components are made of: nickel (silver option) or nickel-plated zinc (gold option).