The MudSling GS_LC for the 2013~14 R1200GS/ADV fits BMW’s stock side cases and most, but not all, aftermarket pannier mounts. It fits Touratech Zega Pro, Jesse, and SW Motech. It does not fit with Hepco Becker mounts.
The photo below shows how Hepco & Becker’s mounts are captured in between the passenger peg and frame lugs with its bracket continuing rearward. This extended bracket interferes with the MudSling side mounting flanges.
Some customers have asked if the mounts could work with some trimming of the MudSling. A work-around may be possible, but we have not attempted it. We endeavored to make the MudSling work with most aftermarket mounts, but had to abandon those that interfered with the most straightforward solution for us.