3M™ CorQUIN Inorganic Insulating Paper, 23 mil, Untrimmed Mill Roll. 3M™ CorQUIN™ Inorganic Insulating Paper is a specialty paper for use in manufacturing spiral wound and other types of core tubes. It can be used in electrical insulation systems up to Class 220(R) per UL 1446 and IEC Std. 60085.