Various thicknesses available (see drop down box).
The 5 packs are sealed and sandwiched with hardboard for protection.
Polystyrol isn't regular polystyrene, it has a much finer density, more akin to the filling in foam board.
Can be used as a printing block – draw on design (in reverse) then depress or cut out any areas not to be printed.
The same principle as used for lino-printing.
Use with any non-solvent based colour medium.