Square D (Schneider Electric) ZB4BV8 Harmony Light Block Assembly. Schneider Electric Harmony™ Complete Body/Light Block Assembly, Series: ZB4, 22 mm Dia, BA9S Incandescent Lamp, 440 to 480 VAC, Screw Terminal, Front Mount, 1.18 in W x 2.36 in D x 1.85 in H. Additional Description: SQD -ZB4BV8 TRANSFORMER LIGHT MODULE 480V. Catalog Description: Harmony XB4, Light block with body/fixing collar, metal, with BA9s bulb, 440 480 V AC.