Found these in a ’Tin’ I kept ‘glow’ plugs in. The ‘NGK’ plug is obviously a purchased one, the other is one made from the body of a burnt out glow plug, a piece of piano, (music) wire And either a piece of Epoxy ‘Stick’ or ‘JB Weld’. I can’t remember if I made a mould for the JB Weld, or used the epoxy stick and ‘Finger’ formed it. The insulator is flush with the end of the body, and sanded flush after curing. This ‘Surface Discharge’ plug worked ok in a modified two stroke aero model engine (Methanol and 20% Castor oil without fouling). The NGK plug would foul. Another possible benefit of The surface discharge plug in a very small engine is no excess volume inside the plug to affect compression etc. If you know people who are into ‘Proper’ RC aircraft, (not electric), or cars, you shouldn’t have a problem obtaining a regular supply of ’burnt out’ glow plugs, saves making the bodies!