A gasket sheet is a large piece of material used to create gaskets, which are small parts that seal two surfaces together. Gaskets are often cut into an "o-ring" shape and are essential for creating airtight and watertight seals in machinery and equipment. 

Gasket sheets are available in a variety of materials and thicknesses, and the best choice for a given application depends on the task the gasket will be performing. Some common gasket sheet materials include: 

• Rubber: A flexible and durable material 
• Cork: A flexible and durable material 
• Nitrile: A commonly used material for sealing oil 
• Neoprene: A good choice for potable water systems because of its chloramine resistance, temperature tolerance, and slow aging 
• Flexible graphite: A material that is compatible with most chemicals and has a high temperature rating. It is also a good heat spreader and EMI shield. 

Gasket sheets are flexible and robust, making them suitable for applications that involve acids, high temperatures, corrosive chemicals, gases, or fluids.