OTAY MESA, San Diego — President Trump flew by helicopter to Otay Mesa Wednesday afternoon for a border wall visit after holding a fundraiser in downtown San Diego. The visit was Trump's first to the border in California since April, when he visited a section of the barrier in Calexico. 

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Trump spent about half an hour at the Otay Mesa border, spoke with Border Patrol agents and admired the tough steel reinforcement fencing. 

“As one of the folks here said it is virtually impenetrable," said President Trump. "It can’t be knocked down. Any walls that are put up, I guess could, but this is very tough.”

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Trump praised the work undertaken on the barrier consisting of concrete and rebar filled steel bollards. Fourteen miles of primary fencing standing at 18-feet tall has been finished while a 30-foot tall secondary piece of fencing is still being built. 

During his visit to the border wall, President Trump said that experienced mountain climbers were used to test out a series of prototypes. He also said the panels at the top of the fencing are designed to absorb heat. 

At the end of the visit, the president walked over to the wall and signed his name on it with a pen. 

San Diego Immigrant Rights Consortium Chair Lillian Serrano called the border visit "political opportunism at its worst."

"To have the president of the United States come to our border town to raise money so that he can further desecrate our way of life is an insult to our communities and to the asylum families in need that he has funneled into the private detention facility in Otay Mesa,'' Serrano said in a statement.

However, there were no protesters in sight during Trump's border visit, but about a dozen supporters showed up to see the president pass by. 

"I'm out here to support our president," said Danny Solis. 

This was not Trump's first visit to San Diego's border. The president traveled to San Diego last March when he visited Otay Mesa to view prototypes of his proposed border wall. During his visit, the president spent about an hour viewing the eight 30-foot-high samples that were built to offer an array of options for the wall Trump has promised to erect along the U.S.-Mexico border. 

Trump’s visit to San Diego is part of a two-day trip to California in which he also held fundraising events in San Francisco and Los Angeles. The president’s campaign is expected to raise close to $15 million for the Trump Victory Fund, a joint committee of the Republican National Committee and the campaign.