Many marine craft are manufactured using composite materials. The outer layer is often a gelcoat, typically 0.5mm - 0.8mm in thickness. Gelcoats are designed to be durable, providing resistance to ultraviolet degradation and hydrolysis. The gelcoat will often carry a pigment that provides the finish colour to the moulded item. Specialised gelcoats can be used to manufacture the moulds which in turn are used to manufacture components. These require very high levels of durability to overcome the mechanical and thermal stresses encountered during the curing and demoulding processes.