Indirect materials include:

materials that are incorporated into the finished product.

materials required for the production process, which do not become an integral part of the finished product.

direct materials that are so insignificant in cost that it becomes unimportant to trace their costs to specific products.

materials required for the production process, which do not become an integral part of the finished product AND direct materials that are so insignificant in cost that it becomes unimportant to trace their costs to specific products.