Abstract: A spark plug adapted, in use, for association with an axial passage (38, 38', 54). The spark plug includes an insulator member (21) having an electrode (23, 23') disposed centrally thereof and projecting outwardly from one end thereof; and an electrode member (28, 47) at said one end of said insulator member surrounding and spaced from said centrally disposed electrode. The electrode member is so shaped to define, with the insulator member a pre-combustion chamber (30) surrounding the centrally disposed electrode. The electrode member has an aperture (29, 49) to receive the extreme end of said centrally disposed electrode of said insulator member. The electrode member further includes a plurality of additional separate apertures (31, 50) adjacent the central aperture (29, 49), and which allow for fluid communication between the pre-combustion chamber (30) and the associated axial passage (38, 38', 54).