great question.
They are not polystone, which in reality is very low cost resin mixed with stone powder as filler .
We use Polyurethane, a thermoplastic polymer based resin.
It is higher in cost, but also very durable,yet not as heavy as Polystone.
Polyurethane is easier to sand, whereas Polystone usually requires some kind of sanding rotary tool.
Hope this answers your question
