DEVMO DC 3V-6V to 400kV 400000V Boost Step-up Power Module High-Voltage Generator

yes they work very well.

Major Warning!!! Treat these modules with respect. They will set you on your you know what if you aren't very careful. A *brief* touch to a 9 volt battery will pop out an inch long spark and a loud snap. They are NOT rated for 9 volts, and operating in that range will destroy them quickly. The dielectric properties of insulation are absolute. Exceed it, and it perforates. Period. I marked the module I tested, and plan to discard it. They are also not rated for high current, so include a (high voltage) resistor in your final circuit. Remember that at 400 kilovolts, it only takes a current of 0.0025 milliamps to produce 1 watt of current. And that would probably be about the limit to these, unless someone wants to do some destructive testing. Quarter watt resistors aren't going to do the job, which is why I said HIGH VOLTAGE resistors. If you don't run them continuously, and don't exceed the input voltage constraints, great. Just don't complain when they stop working.

Works

OMG I just ordered a five piece of these things and they're so cool I feel like a mad Scientist turning it on

These voltage converters work great now, but for some reason when I first got them in the mail, they did not work for 2 days. But when I tried 3 days later, they worked.