The WW1 Heroes Pack comes with the following exclusive items:
-NM-A Type II SMG
-Thompson Annihilator
-Kar98 Trench
-Federov Avtomat
-Imperial Russian Uniform Set
-German Great War Uniform Set
-Japanese WW1 Expeditionary Uniform Set
-U.S. WW1 Uniform Set

Once purchased, kit items are available in both singleplayer and multiplayer, provided CtB is installed. Purchased kits should become available immediately if connected to the official server, otherwise, try restarting the game.

(Note: The picture needs to be and will be updated soon, as it does not display the new uniforms that come with this pack)