5.4.4 CUSHIONING AND VOID FILL5.4.4.1 CUSHIONINGFor cleanroom packaging, cushioning used must be compatible with the cleanroom class. Polyethylene foam is the most commonly used cushioning material.For non-cleanroom or outer packaging, polyethylene or polyurethane foams can be used.5.4.4.2 VOID FILLVoid fill must only be used to fill any gaps in the packaging and must not be used as cushioning for the product.