I have been trying to find info on the roof rack extension bars that came with our latest X-Trail Bonavista. The sellers said they used them for their canoes and skis. The model number is T-051610, and the Nissan dealer said they are made by Thule. I want to sell them as they will not be used by us. I have no idea how they work, or if a key is needed to install them on the existing roof rack. Anyone know anything?? How much should I ask for them?