This kayak dolly is great. The balloon tires roll over any terrain: grass, dirt, rocky surface and especially sand. It's easy to assemble. The tires are square, mounted to wheels and are deflated upon opening the box. Use a bicycle air pump to inflate to 3 lbs each. I highly recommend this and it holds up to 300 lbs. Plus I don't have to tie the kayak down, although straps are included. My wife loves it too. The only downside is our 9.5' kayaks don't have the space to store the dolly in the boat, so we have to lock it up in the vehicle.
Before I bought this, I tried another from Dick's last year and it was horrible. Even with straps, the kayak would fall off before reaching the water.
I highly recommend this Vevor kayak dolly.