The inventive body (8) is provided with a thread (16) on the external surface thereof for screwing said body (8) into a corresponding internal screw thread of an engine and with a gripping area (28) generally embodied in the form of a cylinder having a hexagonal section for gripping said body (8) and screwing a glow plug (2) into a corresponding internal screw thread. The external diameter of the body section between the thread (16) and the gripping area is along the entire height thereof at least equal to or greater than the external diameter of the threaded section (16). Said invention can be used for internal combustion engines, in particular for diesel engines.