The pack contains four 1cm thick foam mats. Each mat is 60cm by 60cm and locks firmly with the adjacent mat with dovetail style joints. The mat is quite sturdy and made of a dense foam like an extra thick exercise mat and the best part is they are only £7.48 for a pack of four mats. So I bought two packs which will give me an interchangeable 2.4m by 1.2 m playing area (or about 8' x 4' for us old folk).
What I intend to do with them is cover them in PVA and sand as a base texture. Then paint them green and add in roads and rivers and maybe a grey industrial/town area. As I will only be playing 6x4 usually this will mean I can get varied terrain layouts by substituting the spare mats and turning them round to get different configurations.
One side of the mats has a rough cloth-like texture, which should help the PVA and sand adhere, while the other side is smooth. So as a bonus I might paint the smooth side blue and then I can flip them over for naval games.