5.0mm white Westfoam foamboard.
Traditionally used for mounting artwork, foamboard great model making and architectural sketch modelling material.
Printed elevations can be spraymounted onto the surface and cut out with a scalpel and safety ruler.
If you are modelling at 1:50 scale, 5mm foamboard is approx the width of an external wall, (3mm for an internal wall).
See our guide to Foamboard Modelling (PDF).