"Liner, Energy Absorbing, for use on the HGU-22 series flight helmet (HGU-2A/P, HGU-22, HGU-26/P, etc). Can also be trimmed and fitted for use on HGU-33 series helmets. Typically used with a TPL Liner, ZetaLiner, or leather fitting pads. Unissued condition. [Medium: P/N 60D4447; NSN 8475-00-061-1323] [Large: P/N 60D4425] ]Extra Large: P/N 60D4363; NSN 8475-00-061-1335]."