A customer purchases items inside the Mobile Field Exchange trailer at the Mission Training Complex at Joint Base San Antonio-Fort Sam Houston. The Mobile Field Exchange, or MFE, is a temporary store housed in a trailer set up by the Army and Air Force Exchange Service that provides a selection of 150 items for purchase to servicemembers and personnel working at the Mission Training Complex, the primary operations center for U.S. Army North, which is leading the Department of Defense response to COVID-19 in the U.S.