Varistors SMD Design Kit (3-48Vrms). Fast response time Low leakage current Nickel barrier for lead free soldering Operating temperature: –40 °C to +85 °C. The Wurth Elektronik WE-VS Design Kit contains a full family of SMD Varistors for DC/DC applications. The WE-VS Kit has sizes from 0402 up to 2220 and are suitable for voltage supplies from 3Vdc - 48Vdc. Applications for the WE-VS kit include: Protection of DC distribution; Protection of power supply; Protection of bus systems and communication lines; Limiting of over voltages; Protection of semiconductors; Surge protection in accordance with EN 61000-4-5; ESD protection in accordance with EN 61000-4-2