When I purchased my first kayak, I actually bought two, so I needed a way to get my new purchase home. The Stacker from Thule came to the rescue. In minutes the kit was assembled and attached to my existing Thule rails on my Prius. One of the really nice features of the kit is it comes with two ratcheting tie downs for the front and rear and two straps to hold the kayak to the rack. I have carried as many as 4 kayaks at once with my Thule Stacker system. On trick I use is to slice a pool noodle down the side and put it over the rails. This gives the kayaks a little cushion and allied me to cinch the straps down tightly. The only downside is that after 10 years or so in the elements some of the components have started to rust. Overall I am very satisfied with my purchase and I recommend it to anyone I meet.