I have recently made up a batch of hills that are designed to complement desert mats such as the Deep-Cut "desert" battle mat on which these are displayed.
The roundish Bathill is 16cm diameter, and the oval Bathill is some 31cm long by 16cm wide. They are both approximately 25mm tall and are made of polystyrene on an MDF base, with a layer of sand glued on top. I've painted, inked and drybrushed the hills and added a coat of matt acrylic varnish, so they should be pretty hard-wearing. If you'd like a pair, they can now be found in the bigredbatshop.
At the moment I only have a limited number of sets, so don't leave it too long!