Originally Posted by
Deeg
That is the vest issued to Special Agents. If you do a Google Image Search for "concealable body armor", you'll see examples similar to what CBP Officers are issued. It's generally the same as a uniformed police officer in the United States wears. (Except in some places like Chicago, where street cops wear vests on top of their uniforms.)
I had assumed, given the commentary about "SWAT," that the OP was referring to a group of agents garbed like the NYPD Hercules teams - visible body armor, helmets, BDUs, automatic weapons, etc.