Schneider Electric XB4BC21 Push button, metal, black mushroom Ø40, Ø22, spring return, unmarked, 1 NO. This Harmony XB4 40mm mushroom head modular black push button operates with a spring return / impulse mechanism. It has a metal bezel. This 40mm mushroom shaped push button is ideal for situations where quick actions are required for a process or machine to function correctly or where operator movements require maximum ergonomy. It is easily installed into standard 22mm diameter cut-outs and connected with simple screw-clamp connections. Its schematic is clearly distinguishable thanks to clear colors and markings, minimizing errors during initial wiring and later maintenance operations. It is impact resistant, dust resistant, water resistant and vibration resistant thanks to its IP66 / IP67 / IP69 / IP69K, making it ideal for operation in harsh environments. Official Schneider characteristics include Range of product: Harmony XB4; Device short name: XB4; Product or component type: Push-button; Bezel material: Chromium plated metal; Fixing collar material: Zamak; Mounting diameter: 22.5 mm; Sale per indivisible quantity: 1; Shape of signaling unit head: Round. Harmony XB4 devices use a chromium-plated metal bezel and are designed for robust panel operation where clear manual control, indication or machine safety interfaces are required.