KY-03 is double fold kayak rack that both side of J bar can be folded down to save most car roof space and adjusted to a perfect angle to fit your watercraft. KY-04 is saddle kayak rack with extra strong and sturdy 4-point gunwale system. Its adjustable arms make loading and unloading much easier. Both KY-03 and KY-04 are for one boat (you can install 2 pairs of KY-03 on one car roof) . KY-06 is designed to carry 2 kayaks with one pair of rack. But it also can be adjusted to fit one kayak or fold down the center handle and make it to fit for larger boat or Stand up paddle boat.