This Harmony ZB, replacement keys (key no.421E) come in a set of 2 keys. This keys set consist of 2 replacement keys to provide a spare option for lock unit that allows a secure manner for authorized staff to operate your machines. It is compatible with standard latching mushroom head push buttons and selector switches units. Specifications Main Product or component type Key Accessory / separate part category Replacement accessory Type of keylock Key Key number 421E Accessory / separate part destination Emergency stop push-button Selector switch Range compatibility Harmony XB5 Harmony XB4 Quantity per set Set of 2 Complementary Product weight 0.031 lb(US) (0.014 kg)