expensive 8 yuan. The price of first-grade Forrest insulation material is 24-26 yuan per cubic meter, and the price of zero-grade Forrest insulation material is 31-34 yuan per cubic meter. The zero-grade Forrest insulation material is more expensive than the first-grade 8 yuan. The trademark of Forrest is owned by Arles Company, and its English trademark is Armaflex. It is a highly elastic closed-cell foamed thermal insulation material based on nitrile rubber, which was invented by Armstrong Thermal Insulation Department, the predecessor of ALEX Company, in 1953.