What's the best fuel for a jet flame lighter?

I’ve been driving myself crazy searching online and I can't find a single thing stating what I actually need to fill this up (propane or natural gas????)
Which one is better to use? I need quick answers here. 😁

Fart in his face 🙏

That’s actually a damn good question. Why? Because they aren't running on your standard butane you'd pick up at a gas station like Shell. 😠