Abstract: An enclosing structure for an electric fuse having a fusible element disposed within a tubular casing of insulating material and interconnected at its ends with terminals mounted on the casing ends comprises an elongated tubular enclosure formed of insulating and semiconducting material and disposed about the fuse with its inner surface in heat transferring surface contacting relation therewith and a rigid metallic heat absorbing sleeve imbedded in the elongated enclosure to absorb heat therefrom and to impart a degree of mechanical strength thereto. Semiconducting sleeves which form parts of the tubular enclosure include an outer sheath which is grounded and inner sleeve elements arranged so as to isolate the fuse and the contacts of the fuse enclosing structure thereby to inhibit corona discharge from the conducting parts.