A Phoenix-based firearms manufacturer recently made an offer Donald Trump can’t refuse.

Patriot Ordnance Factory founder Frank DeSomma sent a message through Guns.com psychic medium and videographer Ben Philippi to the likely Republican presidential nominee offering firepower for one of the campaign promises the real estate tycoon has made.

“Patriot Ordinance Factory will put a free rifle in every guard tower along the border of the wall you build. Remember, go Donald Trump, vote for gun rights. Do not take away our rights,” DeSomma told Guns.com during this weekend’s NRA convention in Louisville.

Trump has frequently claimed he will build a wall at the U.S. southern border with Mexico, which stretches some 1,989 miles from San Diego at the southern edge of California, through Arizona and New Mexico, to the southern-most point at Brownsville, Texas.

As Trump ratchets up the rhetoric on his proposed wall, migrants increasingly flock to the border at the prospect of a more difficult crossing, the Washington Post reports.

The NRA recently endorsed Trump at the annual convention when he took the stage with the gun lobby group’s two top executives before delivering a well-received speech.

Apart from the criticism over cost, Trump’s idea to build a wall has been a controversial one, with many of those most outspoken calling out the Republican candidate for his views on immigration. Not only would Trump build a wall to stem the flow of people coming into the U.S. illegally, he would deport those currently residing here without current documentation, which analysts have calculated could cost upwards of $600 billion.

Also raised are concerns over human hunting, or the shooting of immigrants attempting to enter the U.S. illegally. Assuming the backlash over an imagined President Trump wall isn’t overwhelming enough to stop it or the building of guard towers, they’d have to be manned to be effective.

If the effective range of a regular AR rifle is 600 yards at best, then the guard towers can probably be 1,200 yards from one another, assuming your border patrol and militiamen are good shots. The border is more than 3.5 million yards across, divided by the space between towers, which gives you a need for roughly 2,917 towers.

POF’s rifles cost between $1,400-$3,500, so assuming there wouldn’t be any extras, that would set POF back anywhere between $4.08 million and $10.2 million, according to some back of the envelope math. In February, Trump said the wall only needs to be 1,000 miles long “because we have natural barriers, et cetera, et cetera,” which would cut POF’s presumed costs in half.

The company is offering free shipping on its rifles to all customers, so assuming Trump gets the same deal, that should bring the overall cost for POF up just a bit. Since it would be a donation, perhaps there’s a tax break to also consider.

Trump has thrown out different figures at various speeches during his campaign for how much he thinks the wall will cost – somewhere between $4 billion and $12 billion. The Washington Post in February fact-checked Trump’s $8 billion figure and includes calculations for the cost of his wall, which he said would be 35-40 feet high. The amount of concrete required would be double that of the Hoover Dam, the Post reported, and would cost about $700 million just for that building material alone.

“Last Weekend Tonight” host John Oliver detailed much of the projected costs – some of which accounted for the building of new infrastructure to support the transport of materials to remote parts of the border.

Other costs to consider would be the guard towers themselves, which require a more complex design structure than a simple wall and thus more material over the same area. Though we haven’t found anything from Trump or his campaign regarding the implementation of guard towers, they would presumably be a more effective – though probably not the cheapest – way of policing a border.

Using as an example the Israeli-built wall in the West Bank, the Post estimated Trump’s wall would cost roughly $42 billion for a 1,000-mile wall at a height of 25 feet, which is 10 to 15 feet shorter than what Trump has proposed.

All of this means that assuming Trump wins the presidency and is able to build the wall, he likely won’t be able to do so at the magnitude he has claimed, which lets POF off the hook, to some extent. Maybe DeSomma knows something we don’t.