We use #2 metal (Brass or Nickel) grommets for all our printed banners.
#2 grommets outside diameter: 0.75" (3/4")
#2 grommets inside open diameter: 0.375" (3/8")
Grommets are placed in the corners and 2 to 3 feet apart.
(You may request custom grommet placement on the banners for no additional fee)