We love the Arkel bags, but the nice mounting clamps that come with them are designed for upright bike handlebars, so they extend the bag out quite a ways. When you use bags beside your seat, it's nice to have them in close, to make them easier to reach and to keep the bag within your wheel profile. These clamps bring your bag as close to the mounting tube on your Seatside Mount as possible, so you can adjust the bag to where you really want it. A great way to make a nice bag really nice.
Note that these clamps are sized for our Seatside Mount system, which uses 7/8" (22.2mm) tubes. If you have a different system, it may use different sized tubes, so check first if you don't have one of our Seatside Mounts.