High Quality Content by WIKIPEDIA articles! The U.S. Customs and Border Protection, Office of Field Operations, headed by Assistant Commissioner Thomas S. Winkowski, directs the activities of more than 27,000 employees, including more than 22,000 CBP Officers and Agriculture Specialists, and oversees the programs and operations at 20 Field Operations offices, 327 ports of entry, and 15 preclearance stations in Canada, Ireland, and the Caribbean.