When he makes his first presidential visit to California on Tuesday, Donald Trump will see prototypes of the wall he wants to build on the border with Mexico to help control illegal immigration.

A demonstrator writes on symbolic wall as is seen a pinata representing the U.S. President Donald Trump during a protest outside the U.S. embassy, in Mexico City, Mexico January 20, 2017. REUTERS/Edgard Garrido – RTSWLX4

Here are facts about the mockups and Trump’s plan:

-Eight full-scale models stand side-by-side up to a height of about 9.8 yards (nine meters)

-The prototypes tower over the existing graffiti-covered border fence near hills on the edge of San Diego, at the border with Tijuana, Mexico

-They are colored beige, brown and gray.

-Some have rounded tops, in varying thicknesses to prevent climbing. One panel has a slanted anti-climbing barrier.

-Six US companies built the prototypes, most from reinforced concrete and the remainder from other material.

-The structures were unveiled in October.

-The mockups are assessed for their anti-breaching, anti-climbing and anti-digging capabilities.

-Each prototype section cost more than $300,000 and, according to some estimates, the complete wall could require an expenditure of up to $20 billion.

-The border with Mexico stretches nearly 2,000 miles (3,200 kilometers), about a third of which already has some type of barrier or wall.