FWIW the 41L KTM branded Tourtech panniers will just barely hold a Medium or Large full face helmet [10.5 inches wide]. The lip at the top of the bag is narrower than the body; just guessing about 0.25 inches on each side but I haven't measured it. The downside is they are much wider than the bars. The 41L bags are about the same total width as the Gobis but with more storage capacity. I doubt the 35L Alu panniers [9 inches wide] will hold a FF helmet if that is important to you.