For the older 3M Speedglas Welding Filter models: 9002X/9000XF.
Format 53 x 103 mm.
Most important features
The inner cover is designed to protect the inner surface of the filter from sparks and splashes. Can be used to darken the shade of the welding filter by 2 degrees.
If you use the welding filter without an inner protective glass, the warranty will be void if sparks or splashes damage the glass.
Clean regularly with a soft cloth and replace if there are pits or scratches.