These hex pieces are precision laser cut from 1/8" (3mm) MDF, not the brittle foam material you may be used to seeing from other manufacturers.  You can add foam to the top of these hexes to create elevated terrain (hills, etc) and still have a durable MDF base that will stand up to years of continued use.

Some hexes are shown with paint and ground covering applied, this is for demonstration purposes only. Hexes are supplied unpainted and without ground covering and trees.