Unlike their 0-7 counterparts in the Army and Air Force, Brigadier Generals in the United States Marine Corps and Rear Admirals (lower half) in the Navy and Coast Guard are not given a choice in the size of the stars used as insignia of grade worn on collars and caps: 9/16” is the only authorized size in all three services.
On collars, Navy and Coast Guard regulations call for the star to be placed one inch from the front and lower edges of the collar with a single ray of the star pointing toward the neck, positioned so that an imaginary line bisects the star and the collar point. On Marine Corps uniforms with the khaki shirt, the star is centered between the top and bottom edges of the collar and placed an inch from the front edge of the collar; a single ray points at a right angle to the top of the collar.
Marine Corps Officers must wear Collar Rank Insignia at all times when they are wearing the Service “A” Uniform, with the insignia centered between the top and bottom edges of the collar and the outer edge of the insignia one inch from the collar’s front edge. On USMC Garrison Caps, the star is worn on the right side with a single ray pointing up and the flap bisecting the insignia.
For Navy and Coast Guard Garrison Caps, the insignia is also worn on the right side and is positioned 1.5” from the bottom of the cap and 2” from the front crease.