Most current Thule kayak racks & surfboard racks include universal mounting hardware that enables them to attach directly to Thule Aeroblade Loadbars, Thule 500XT Xsporter and Whispbar Roof Racks as well as to most factory installed crossbars. However these racks will not attach to the Thule PRO Series Rack systems without the use of the Thule Xadapt3. The Thule kayak racks that require the Thule Xadapt3 kit when used on the Thule PRO commercial truck racks and van racks are: 887 Slipstream, 835PRO Hull-a-Port, 835XTR Hull-a-Port, 830 Stacker, 878XT Set-to-Go, 875XT Hydro-Glide, 883 Glide & Set, 881 Top Deck and 839 Get-a-Grip paddle/mast holder. The Thule 593 Wheel-On bike wheel holder and Thule 554XT Hang-Two surfboard rack also require the Xadapt3 kit. The Thule 897XT Hullavator kayak rack attaches directly to the Thule Pro commercial van rack & truck rack bars - no adapters required for 897XT Hullavater. The Thule 877XT Rollercoaster kayak rack and Thule 579XT canoe rack are NOT compatible with Thule PRO commercial truck racks and van racks.