Many soldiers in the Marines and in the Army will have a M9 Bayonet made by Buck Knives with them.
Some basic info on it:
Bowie-style clip point, fuller on right hand side, rounded retangular through hole rather close to the point, black oxide finish optional, steel (alloy N/A) tempered to 56-58 HRC, circular cross-section xytel handle, muzzle ring in the guard, pommel fitting mates with the M-16A2 bayonet lug.
Overall length: 12 1/4"
Blade length: 7 1/8"
Weight: 14 oz
The issue cordura and plastic sheath comes with a sharpening stone and a mechanism that mates with the hole in the blade to form a wire-cutter.
(Ref: James Marchington, Knives: Military Edged Tools and Weapons, Brassey's, UK, 1997.)