The bushing on the mica base is made of mica on an alumochromophosphate or alkali binder with a heat resistance up to 500 °C. They are used for electrical insulation of current conductors operating at high temperatures. The internal diameter is 5-70 mm, the outer diameter is up to 75 mm, the length is 25-850 mm, the wall thickness is 0.5-15 mm.