I hesitated before choosing this item due to some poor reviews. I was looking for strong but low profile wheel trolleys for my Jaguar XJ, not the lightest of cars. As I have a single width garage I needed to push the car right over to each side as I worked on the wings, removing doors etc. These were easy to assemble, one slim spanner is supplied to get under the plate to hold the wheel spindle while you tighten the nut with your own standard spanner or socket. The castor wheels are of hard plastic and strong 'forks' and bearings that control each wheel. Two of the four on each trolley are locking wheels. My concrete floor is not smooth, it has the ridges where they use the edge of a wooden plank to flatten the concrete before it sets. So I expected a bit of exertion to move the car. The instructions advise you set the castor wheels in the direction you want to go. Good advice as with just a little help from my trusty helper we managed really quite easily to get it moving. I was pleasantly surprised. And worth another mention, because these are of low profile you are not jacking the car up very high to get the trolleys under the wheels. The side bar handle is good for handling the trolleys too. I think these are the best available here and a good price.