This product has good electrical insulation properties, arc resistance and arc extinguishing properties.There are three types of products: 1.they are all vulcanized fibre tube. 2.The outer layer is kraft paper, The inner layer is vulcanized fibre tube. It is a composite material. 3.The outer layer is fiberglass,The inner layer is vulcanized fiber tube. It is a composite material. This product applies to: "K" type high-voltage fuse link "T" type high-voltage fuse link "F" type high-voltage fuse link Capacitor dedicated fuse link