All 8 Prototypes Of Donald Trump’s ‘Big, Beautiful’ Border Wall [PHOTOS]

Nine months after taking office, President Donald Trump appeared to be keeping one of his central promises he made during his campaign. The president's U.S.-Mexico border wall has taken a significant step toward becoming a reality with the debut of its eight finished prototypes Monday, which was seen, assembled near the existing fence along the U.S.-Mexico border miles outside San Diego, NBC News first reported.

The samples of Trump's border wall which measure between 18 and 30 feet in height will be tested to see which would best fit in Trump’s construction scheme, U.S. Customs and Border Protection (CBP) officials said.

Four of the prototypes are made from concrete which will be tested in order to be used for the concrete portions of the wall. The remaining four are made of non-concrete materials, which will be used in areas where the barrier can be seen through, the officials said.

"We’re going to test it for breachability. For the subterranean aspect," Roy Villareal, the Deputy Chief Patrol Agent of the San Diego Sector of CBP, told NBC News. "Can we dig under it? Can we cut through it? Can we scale it?"

According to a rendering that has been released by CBP officials, the wall has been envisioned to be a multi-faceted barrier that would likely feature a concrete stretch facing the United States and a non-concrete stretch facing Mexico, which would allow officials to see through it, NBC News reported.

However, even with the progress of the wall, the important question over how Trump plans to pay for everything remains unanswered. The president has said multiple times that Mexico would pay for it but Mexico mentioned several times that it will not.

The White House’s proposed budget in 2018 seeks $1.8 billion in order to build new sections of the wall and replace existing ones. This money would also be used to pay for more than 40 miles of new wall. However, a problem persists as White House officials believe the entire wall project would likely cost between $8 and $12 billion, although the internal assessments by the Department of Homeland Security suggest that it could be even higher.

There is also another question that has been raised about the effectivity of the wall. Villareal acknowledged "It's hard to gauge" whether just a massive wall would cut historically-low apprehensions along the U.S.- Mexico border.

"There's always going to be some form or crime, or in this case, illegal migration," he said.