This specification classifies materials into classes and grades according to cushioning performance. Class numbers represent static loading ranges:

• Class 1Below 0.08 psi
• Class 20.08 - 0.2 psi
• Class 30.2 - 0.5 psi
• Class 40.5 - 1.0 psi
• Class 51.0 - 1.5 psi
• Class 61.5 - 4.0 psi
• Class 74.0 - 10.0 psi

Grade letters indicate maximum g's allowable for loading range indicated by the class number (24-inch multiple drop):

• Grade ALess than 20 g's
• Grade BLess than 40 g's
• Grade CLess than 60 g's
• Grade DLess than 100 g's
• Grade ELess than 130 g's

To determine compliance, go to cushioning curves. For example: What thickness of ETHAFOAM* 220 polyethylene foam would meet the requirements of Class 4, Grade C?

• Class 4 has a loading range of 0.5 to 1.0 psi
• Grade C= below 60 g's
• For ETHAFOAM 220 polyethylene foam, 24-inch multiple-drop curves show that thickness of 2 inches and higher stay below 60 g's over the 0.5 to 1.0 psi loading range and would, therefore, be acceptable

Other property requirements in this specification are not detailed here.  ETHAFOAM brand plank products currently meet the other property requirements in this specification.