The inner cover plate is designed to protect the inside surface of the filter from spark and spatter. Can be used to increase +1 dark shades of the welding filter.
Failure to use an inside protection plate with the filter voids the warranty if spark or spatter cause damage to the glass.
Regularly clean with a soft cloth and replace if any pits or scratches occur.
For the older 3M™ Speedglas™ Welding Filter models: 9002X/9000XF. Size 53x103 mm.