This Harmony XB5, black add-on square trim is used to give a square appearance to circular head. This add-on square trim is designed as a simple way to give a square appearance to ZB5A circular heads and is clearly distinguishable visually at a distance thanks to its clear color. It is compatible with Harmony XB5. It is designed to fit with a standard 22mm control and signaling units, ensuring compatibility when installing in pre-existing machinery.