This Harmony XB4 replacement key (key no. 4A185) comes in a set of 2 keys. It is compatible with the Harmony XB4 and XB5 latching mushroom head buttons and selector switches. This key set consists of 2 replacement keys to provide a replacement option for the locking unit, allowing a secure way for authorized personnel to operate your machines. It is compatible with the standard latching mushroom head buttons and selector switches.