In this case, we will use an ESD gun (esd simulator) to detect the electrostatic immunity of the product. For civil electronic products, we generally recommend EMCSOSIN 20KV ESD gun (ESD 20K). In the standard of IEC/EN 61000-4-2, GBT17626.2, the highest level of air discharge is 15KV, so 20KV is enough for us.