Soviet anti aircraft fire became an almost assured death  sentence to German pilots during the Russian campaign. Bomber crews were outfitted with extra protection to enhance  survivability. Some M35 style helmets & more  commonly M40 helmets were produced and altered  allowing for use of headphones. In terms of the  Allied effort using the M3 Armored helmet for  bomber crews, the  Luftwaffe Flak was the best German  equivalent and almost exclusively used on the  Eastern Front.  The features of the ear cutouts would have made this an excellent Infantry helmet as it does not inhibit hearing.