This kayak rack offers the ultimate in carrying performance. With its 4 boat capacity and proven universal mounting system, The Stacker is the most efficient way to carry multiple kayaks and paddle boards.FEATURES – Upper bridge design makes tying down boats easier than ever- Universal hardware for easy transfer from vehicle to vehicle- Mounting brackets clamp to existing load bars and roof racks- Folds down flat for a cleaner look when not in use- 1 Pair of ratcheting tie downs, 2 straps, and buckle protectors included- Holds up to 4 kayaks- Fits Thule square, Rapid Aero and AeroBlade load bars; Yakima bars; and most factory installed luggage racks- For Thule Xsporter load bars, the Xadapt3 (THXADAPT3 – sold separately) is required for installation