GEWA Viola Case, Concerto, Oblong, Adjustable 36-42.5cm Body has a Liquid 2K-PUR foam  injected under heat into a mold. After expanding and curing, the shell can be lined on the inner. On the outer usually a water resistant layer is used. Even wood screws can be fixed in this dense and hard material. By adjusting the two chemical components the mechanical properties can be adjusted.