Master sergeant
A master sergeant is the military rank for a senior non-commissioned officer in some armed forces.
Israel Defense Forces

Rav samal rishon
insignia
The רב-סמל ראשון rav samal rishon (abbreviated: "rasar") (master sergeant) is a non-commissioned officer (נגדים) rank in the Israel Defense Forces (IDF). Because the IDF is an integrated force, they have a unique rank structure. IDF ranks are the same in all services (army, navy and air force). The ranks are derived from those of the paramilitary Haganah developed in the British Mandate of Palestine period to protect the Yishuv. This origin is reflected in the slightly-compacted IDF rank structure.
United States

Master sergeant insignia
U.S. Army

Master sergeant insignia
U.S. Marine Corps

Master sergeant insignia
U.S. Air Force

E-7 First sergeant insignia
U.S. Air Force

Obsolete
master sergeant insignia
U.S. Air Force
(until 1991)
A master sergeant is: