>>11491546
This looks more like....

guys correct me if my knowledge has run out here, but this looks like ~pressed foam board~ aka the kind of thing they occasionally make cheap robot kits out of, where you punch out the pieces, fold them along the pre-scored parts, and connect them to ball joints.
If you can actually just chop pieces out of it, it's too soft, that much is for sure. So yeah I'd say the thin plates of real actual hard styrene. I mean if you can get thicker ones, awesome, but then cutting through them becomes harder. They're not that bad though, basically gunpla material.