The second type of insulation is a spray on foam (e.g. polyurethane solid foam insulation). New dashboard consisted of aluminium body and two pieces of soft polyurethane foam padding. Shock pads are made of polyurethane and rubber. Casper mattresses consist of four types of foam, memory foam, and polyurethane support foam. Also used as a stabilizer in the manufacture of polyurethane foam. A typical design is an aluminium frame with blocks of polyurethane foam attached to it. Water can be simulated using polyester casting resin, polyurethane, or rippled glass. Synthetic sponges can be made of polyester, polyurethane, or vegetal cellulose. Varnish may also be created from synthetic resins such as acrylic, alkyd, or polyurethane. Dinitrotoluene is the precursor to toluene diisocyanate, which used in the manufacture of polyurethane foam. Plastic lenses are typically made from acrylic, polycarbonate, CR-39 or polyurethane. It is used in the production of flexible polyurethane foams. Memory foam, like other polyurethane products, can be combustible. They are usually made of polyurethane or silicone. In 1960 more than 45,000 metric tons of flexible polyurethane foams were produced.