4.500 inch inside diameter; keeps head in straight neutral position
NSN 5965-01-561-7560
NSN 6130-01-492-4307
NSN 6220-00-250-8580
NSN 6240-00-518-3541
NSN 7035-00-300-3208
NSN 6150-01-625-3104
NSN 5975-00-912-0619
NSN 6320-01-445-5893
NSN 5965-01-069-0391
NSN 6130-01-445-6365
NSN 6240-00-594-7138
NSN 5990-01-171-3547