When sourcing SMD Varistors (Surface Mount Device), you must prioritize Varistor Voltage (Vn), which is the voltage at which the device begins to conduct. Additionally, evaluate the Maximum Allowable Voltage (AC or DC) to ensure it exceeds the normal operating voltage of your circuit. For high-speed data lines, Capacitance is critical; low-capacitance models are required to prevent signal distortion. Finally, check the Peak Surge Current (8/20μs) rating to ensure the component can withstand the expected transient energy in your specific application.