Fabric expansion joints are used to give flexibility in large thermal movements in a small space. They isolate noise and are made in a variety of materials and designs and have no definite size restrictions. Typically, fabric expansion joints are separated into three types. Elastomeric joints are made of high strength fabrics which may have wire reinforcements that are melded with elastomers like neoprene or silicone. They are used in flue gas desulfurization systems or in wet or corrosive environments. Composite fabric joints are another type of fabric joint designed for use where the temperature is continuously hot. They are made up in layers that include a gas seal membrane, insulating layers, an insulation retaining layer (when temperature exceeds the range of the seal membrane) and a flange gasket. Fluoropolymer fabric joints are used when the system they're in is wet and temperatures rise to 600 degrees Fahrenheit (and occasionally higher).