Schneider Electric ZB5AX2 Harmony Pushbutton Head Brand: Schneider Electric. Part Number: ZB5AX2. Schneider Electric Harmony Square D Pushbutton Head, Mushroom Non-Illuminated Push-Pull Latching Standard Unmarked, Series: ZB5, 22 mm Size, Round Shape, Plastic, Black. Additional Description: SQD -ZB5AX2 BLACK MUSHROOM LATCHING HEAD PUSH-PULL 6. Catalog Description: Head for non illuminated push button, Harmony XB5, black mushroom 60mm, 22mm, latching, push-pull to release, unmarked..