Musk, CEO of the Boring Company, Tesla, and SpaceX, said on Thursday that the flamethrowers should be coming in two weeks, tech news site Engadget reported. Delivering the flamethrowers, he said, was complicated by the fact that the flamethrowers are loaded with propane. You can only ship limited quantities of propane through the United States Postal Service and it can’t be shipped airmail or internationally at all. Musk said they will instead be delivered by a Boring Company delivery van.

Musk’s oddball sale of the flamethrowers started in January as a gimmick to help sell Boring Company hats. At one point, he posted a video on Instagram of him playing with a flamethrower ahead of the product’s release.

After 50k hats, we will start selling The Boring Company flamethrower

— Elon Musk (@elonmusk) December 11, 2017

Musk ended up selling out of the 20,000 flamethrowers that were available for pre-order for $500 each. That means Musk has sold at least $10 million in flamethrowers before they sold out, at which time the price was raised to $600. The flamethrowers will be shipped with complimentary fire extinguishers, according to Musk.

On top of delivery problems, Musk also faced backlash from a California lawmaker over the safety of the devices. However, Musk said that the flamethrowers are legal and abide by the Bureau of Alcohol, Tobacco, Firearms and Explosives’ standards.