 On April 25, 2007, SgtMaj Estrada stepped down from his post as Sergeant Major of the Marine Corps.Aside from Sergeant Major of the Marine Corps, master gunnery sergeant (MGySgt) and sergeant major are the highest enlisted ranks in the Marine Corps; however, there are far fewer master gunnery sergeants than sergeants major.One of the major differences between the two E-9 ranks is that master gunnery sergeants retain their Military Occupational Specialty (MOS), while sergeants major are given a new MOS to reflect their general command focus.