This Harmony XB4 spare key (key no. 8D1) is supplied in a set of two keys. It is compatible with the Harmony XB4 and XB5 latching mushroom-head push-buttons and selector switches. This key set consists of two spare keys to provide a spare option for the locking unit, which allows a secure manner for authorised personnel to operate your machines. It is compatible with the standard latching, mushroom-head push-buttons and selector switches.