Abstract: A heating unit combining a block of thermal and electrical insulating material and a pair of electrical resistance elements in which the block contains a mass of ceramic fibers bound together and has an elongated slot with confronting walls rising to the surface of the block from opposite sides of a floor, and the resistance elements are in the form of thin members constructed of continuous resistance wires which are provided with opposite bends to form a serpentine shape, the bends being embedded in the opposite walls of the block to secure the electrical resistance elements on the block adjacent to the floor of the slot.