Trump visits border wall prototypes: What you need to know

President Donald Trump traveled to San Diego, California, on Tuesday where he will visit eight border wall design prototypes.

The president took a jab at the Golden State’s sanctuary city policies, which he called “illegal and unconstitutional,” saying they put “the safety of the entire nation at risk” and “must stop.” Stemming the flow of illegal immigrants into the U.S. has been a primary influence behind the president’s push to build a wall along the southern border.

The eight prototypes, selected by Customs and Border Protection, are the work of six companies, including Alabama’s Caddell Construction, Texas Sterling Construction Co. and Maryland’s ELTA North America Inc., the latter of which is an Israeli-owned defense contractor and the only international company to win a bid.

Half of the eight designs are made of concrete, while the other four are comprised of different materials, including metal. All are 30 feet tall, and must extend 6 feet below the ground.

The border wall prototypes have been tested for a number of characteristics, including how easy they are to dig under or climb over, and how safe they are for Border Patrol agents.

Contractors had 30 days to build their models at the testing site, and each design costs between $320,000 and $490,000, according to The Washington Post. Some have different characteristics, depending on which side it is viewed from, including one that has metal spikes on Mexico’s side and a brick pattern on the other.

Customs and Border Protection said it will evaluate each of the designs to help inform future construction ideas, meaning that a singular prototype design may not be chosen as a designated “winner.”

Trump has said Mexico would pay for the wall along the countries’ shared border. However, Mexican officials have repeatedly opposed those suggestions. Meanwhile, the administration’s proposed 2019 budget allocates $18 billion toward construction of the border wall.

While in California on Tuesday, Trump will also speak at select military bases.