The inner cover plate is designed to protect the inside surface of the filter from spark and spatter.
Replace anytime the plate becomes deeply pitted, scratched or too dirty to clean with soft cloth or lens paper.
Regularly clean with a soft cloth and replace if any pits or scratches occur.
For 3M™ Speedglas™ older welding filter models: 9002X/9000XF filters. Size 53x103 mm. Plate marking 42 02 10, pkg of 5.