"When the zombie apocalypse happens, you'll be glad you brought a flamethrower," Musk tweeted.
The flamethrowers are available for pre-order at $500 each, which doesn't include the optional $30 for a matching fire extinguisher.
Musk assured consumers on Twitter that he wan't trying to mastermind doomsday to generate sales.
Musk, who tweeted that there are 20,000 units, has been giving a timeline of the sales.
The profits of the amount sold don't include the potential numbers from fire extinguisher sales.
The Bureau of Alcohol, Tobacco, Firearms and Explosives does not regulate domestic production and possession of flamethrowers, the ATF said in a statement to ABC News.
California requires residents to have a permit for possession of a flamethrower.
However, Maryland outlawed flamethrowers, where they are considered a "destructive device."
When Musk was asked on Twitter about the product's legality, he said: "ATF says any flamethrower with a flame shorter than 10 ft is A-ok." The company said in a statement that its product is shorter than 10 feet.
And then on Twitter, he said his company's flamethrower was the "world's safest."
Boring will ship flamethrowers out in the spring, according to their website.
The idea of Musk selling flamethrowers seemed to originate when he promised his Twitter followers he would do so if Boring sold 50,000 hats.
The Boring Company is primarily an infrastructure company that Musk started as part of his vision to elevate traffic in congested cities, like the Los Angeles area, by building underground tunnels.
Musk has filed a permit to dig a tunnel within Los Angeles city limits in Nov. 2017.