This Harmony ZBY marked legend has black background and is marked with “O” lettering.It is compatible with Harmony XB4 and XB5 push buttons and pilot lights.This legend provides clear labelling for your push buttons.It is supplied ready engraved with a marking relevant to machine operation and is compatible with any standard 22mm Harmony control and signaling units.It provides clear and resilient symbol marking on the label, with high contrast.