Eight towering constructions of concrete and steel stand in the border patrol enforcement zone in Otay Mesa.
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The prototypes were built in the shadow of the current fence and a neighborhood in Tijuana.
U.S. Customs and Border Protection says these models could replace its aging infrastructure.
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"This was built in the mid to early '90s," said Roy Villareal, the chief of the border patrol's sector in San Diego. "In the last three years our secondary fence has been breached almost 2,000 times. So is there a need for improvement? Absolutely."
Following up on the president's campaign promise to "build the wall," the Department of Homeland Security is funding the work of six private contractors building the prototypes. They are: W.G. Yates & Sons Construction Company, ELTA North America Inc., Caddell Construction Co., Texas Sterling Construction Co., KWR Construction and Fisher Sand & Gravel Co.
There are four prototypes made of concrete, the other four of alternate materials.
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CBP says each came under its budget of $50,000. Features range from open slits, sharp metal on top, to different colors on each. Agents use cameras and other technology in the border patrol enforcement zone. They say a new wall would only help their ability to curb illegal activity.
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"Whether it's illegal immigration, narcotics smuggling, whatever that threat may be, this should serve to deter that, hopefully put an end to it," Villareal said.
The protoypes are being built just steps away from the current border wall in San Diego.
The most obvious difference is the height. The current primary wall is 10 feet tall and, the secondary stands around 18 feet. Most of the proposed new walls are pushing 30 feet.
Testing of the prototypes is set to begin at the end of next month. CBP won't say how or how many options they will pick.
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Among the factors: "The ability to dig underneath it, the penetrability, the aspect of being able to breach in someway or degrade the prototype and scalability," Villareal said.
Congress would still need to approve funding for a new border wall.
Trump's 2018 budget asked Congress to approve $1.8 billion to begin building parts of the wall.
There are critics of the prototype project including groups that advocate for immigrant rights.
"Absolute waste of money, it's a boondoggle meant to satiate this idea that the president promised a border wall," said Pedro Rios, the director of the U.S.-Mexico Border Program for the American Friends Service Committee. Rios says the focus needs to be on the immigration system, not the wall.
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