8/15/2012 - Electronics Technician First Class Petty Officer Sean McKenzie, Nuclear Power Training Unit and chief petty officer selectee, tries on a Navy service dress white uniform, commonly referred to as choker whites August 14, 2012, at the uniform shop at Joint Base Charleston - Weapons Station, S.C., while Master-at-Arms Chief Petty Officer Marvin McDonald, NPTU, ensures he has the proper fit. Selection for promotion to chief petty officer requires selectees to purchase a new "sea bag," which consists of new khaki and service dress uniforms. (U.S. Air Force photo/ Airman 1st Class Chacarra Walker)