... 4.protect electrode 5.high voltage resistance High purity&heating-resistanceOD range 1.2mm-360mm, Silicon Dioxide>99.995 ... iron outside, calcium, magnesium, potassium, sodium, lithium seven impurity elements of the total content of not greater than 100 x ... ,milky-white,red,u-shape,twin tube, special shape, etc.4. OEM allowed5. certificate :CE6. application fields:heating element, drying equipment, ...