Specialist is the fourth progressive enlisted rank in the UNSC Army and the highest non-NCO enlisted rank. It is in the E-4 grade. A Private First Class is usually promoted to Specialist after showing technical proficiency within a given field. It is equal in grade to Petty Officer Third Class in the UNSC Navy, Senior Airman in the UNSC Air Force, and Corporal in the UNSC Marine Corps. UNSC Army Corporals have equivalent pay and grade to Specialists, but since Specialists are not NCOs, and Corporals are, Corporal is slightly higher than Specialist. Specialists rank above Private First Class, but rank under Sergeant. The main difference between Specialists and Corporals is that Specialists provide technical leadership while Corporals provide command leadership. A PFC will normally be promoted to Specialist, and then directly to Sergeant. However, PFCs who are being given a leadership position earlier than normal will go to Corporal, since Specialists cannot lead troops.