Square D (Schneider Electric) ZB4BVJ3 Harmony Light Block Assembly. Schneider Electric Harmony™ Light Block Assembly, Series: ZB4, 22 mm Dia Size, LED Lamp, 12 VAC/VDC, Screw Clamp Terminal, Panel Mounting, Green, 1.18 in W x 1.46 in D x 1.85 in H Dimensions. Additional Description: SQD -ZB4BVJ3 12V PROTECTED LED LT MODULE/GREEN W/BASE MODULE/GREEN W/BASE. Catalog Description: Harmony XB4, Light block with body/fixing collar, metal, green, integral LED, 12 V AC/DC.