This is a cellulose based paper which is widely used for conductor insulation in oil filled transformers. There are various grades of cellulose paper such as:

Kraft paper:

• Thermal class E (120º) as per IEC 554-3-5 in thickness from 50 to 125 microns.
• Thermally Upgraded paper Thermal class E (120°) as per IEC 554-3-5 in thickness from 50 to 125 microns.
• Diamond dotted Epoxy paper in various thicknesses. This improve thermal properties as compared to normal Kraft paper.