When sourcing manual disconnect switches, you must prioritize Voltage Rating (Ui/Ue) and Current Capacity (Ith/Ie). Ensure the switch can handle the maximum system voltage (e.g., 600V or 1000V for PV systems) and continuous load current. Additionally, verify the Short-Circuit Withstand Rating (SCCR) to ensure the device remains safe during electrical faults. For industrial applications, look for high-grade flame-retardant materials (UL94-V0) and silver-alloy contacts to minimize contact resistance and heat generation.