A helmet liner that is infinitely adjustable by the user in the field is provided. The helmet liner includes front, center and rear cushioning portions with integrally formed spaces between the front and center portions, and the rear and center portions. The integrally formed spaces provide the liner with the ability to independently flex [in one degree of freedom] and bend [in a second degree of freedom] to collapse the spaces without any overlapping of cushioning portions and thereby conform the liner to the hemi-spherical shape of the wearer's head. The spaces provide ventilation for the wearer's head. The helmet liner may also provide for variable thickness of one or more of cushioning portions as well as antimicrobial treatment of the fabric. By increasing the thickness of the rear cushioning portion with respect to the front cushioning portion, the number of optimum fits achieved by the liner is maximized, while biasing the wearers head toward the front of the helmet, thereby increasing the wearer's field of view (FOV).