Originally Posted by DeweyCheathem

While not officially so, the FMM180 is actually treated as a re-usable multiple use tourism card for frequent crossers by the Mexican border patrol in San Ysidro, and they won't make you surrender it before leaving MX, so you can use it again and again crossing back into Mexico. I bought mine about 4 weeks ago and have used it multiple times, including for my TJ to SJD trip this week.

The FMM180 can be gotten in person at the San Ysidro crossing or online, as well as at CBX. I don't know if they make you surrender the FMM180 coming back into the U.S. via CBX. They certainly do not when crossing back into the U.S. via San Ysidro