These units when placed beneath a tyre, reduce the tendency of tyres, when left standing for some time, to get flat spot on them. Whilst this applies to caravans, RVs or boat trailers standing on concrete for some time, it also applies to seldom-driven cars (such as classic cars) just sitting in your garage. You simply place them on the ground and drive onto them. It is better if you anchor them in place with a masonry screw. Suitable for most tyre diameters. If product is not wide enough, lay two side-by-side. 

Dimensions: 460(L) x 210(W) x 60(H)mm