Standard: according to GB/ T 11718-1999: 1) Density : 450-880kg/ m³ 2 Moisture 4-13% 3) Modulus of inner combination( MPA) > = 0.45 4) Modulus of surface combination MPA) > = 1.2 5) Tolerance of length ( width) : + -2.0MM 6) Tolerance of thickness: > 19MM-- + -0.3MM,