The M42 differs from its predecessors primarily in its simplified and more cost-effective manufacturing process. While the helmet edges of the M35 and M40 were elaborately rolled inwards, the edge of the M42 remained sharp and slightly flared outwards. Furthermore, the ventilation holes of the M42, as with the M40, were punched directly into the helmet shell, instead of being used as separate, riveted bushings as in the M35.