A cartridge type heater is provided with at least one hot wire coil (13), which has two coreless coil strands (11, 12), which extend in an insulating material (50) along the two sides of a carrier wall (14). The heater includes an insulating material that is coordinated with the internal diameter of a metal jacket (2). The hot wire ends (9, 10) are provided with terminals projecting from the same end of the metal jacket (2). The hot wire coils (11, 12) are electrically connected to one another in the area of an end edge of the carrier wall (14). This edge is located in the closed end area of the metal jacket (2) and the coils are guided by spacers (45) distributed at the longitudinal edges of the carrier wall (14). At least the terminal-side end of the dimensionally stable carrier wall (14) is provided with an attached coil holder (15, 15/1), to which the hot wire ends (9, 10) are fastened under tensile stress. This keeps the windings of the hot wire coil (13) spaced apart from each other. At least one filling opening (42) is provided for the granulated insulating material (50).