Do mods like CB, OW, DS stack?

[Bulgarian]

For example if you carry 2 griefs, does that give you a total of 40 DS for both or 20 for each?

[Ce Olba]

For example if you carry 2 griefs, does that give you a total of 40 DS for both or 20 for each?

20 each.

CB, DS and OW, when in weapons, only apply for the weapon they are in.