Kayak carts..

...and they work great!  But Mark is right.  They were selling "blems" at the time and apparently they don't have any at the moment. 

The 'fat' tires seem to work fine on most surfaces.  They're even good for stairs.  My only dissatisfaction is that they're pretty wide.  Could be a problem on narrow trails.

As far as durability, they come with a little "repair kit" of vinyl pieces to patch any holes.

Randy

If you aren't concerned about weight, wheelbarrow tires are much cheaper and comparable in performance.  My cart may be heavy, but I could tow my kayak on it behind the car all the way home if I had to. 

We have drug our gray Roleez wheels over a variety of surfaces and they have proven to be very very durable, no leaks of any kind to date.  Expensive, but they do perform very well.