The figures are somewhat flexible, very similar to AT-43 figures. If I had to guess, I'd say they were made of the same plastic material. They are less flexible than WOTC Star Wars or Wizkids Heroclix, but more flexible than GW plastics. I've got two of the starter boxes and seen a couple of others, and thre always seeme to be at least a few weapons on the figures that are warped. However, they can be straightened with a little hot water.
The mechs are more like standard model styrene plastic. I'd say it's comparable to Tamiya or Dragon kits.