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Chrome and Smart Keys look similar, but Chrome Keys belong to newer Mercedes cars. Chrome Keys have a metal casing, but Smart Keys are generally made of plastic. Although Chrome and Smart Keys operate in a similar way, their batteries are changed in different ways. The current Chrome key model has a red triangle for its panic button. The words "panic" should be written on this button in capital letters. If you have the latest Chrome key, purchase one CR 2025 battery before you open its case. All Chrome key batteries are changed in the same way, but older models need 2 CR 2025 batteries instead of one. Unlike newer models, older Chrome keys have a circular panic button with the word "panic" inscribed in white letters. Newer and older Smart Keys will have a black plastic casing. Although all Smart Key batteries are changed in the same way, newer Smart Keys have a red panic button identical to older Chrome keys while first model Smart Keys do not. Smart Keys need 2 CR 2025 batteries. The first Smart Key model does not have a panic button.
Distinguish between a Chrome or Smart Key. Spot the latest Chrome model by its red triangular button. Look for a circular panic button on older Chrome keys. Check for a plastic casing on Smart Keys.