NGK Y-721RS / Y721RS / 3687 Sheathed Glow Plug Genuine NGK Component ( 3687 )The central function of glow plugs is to provide additional energy for the start. Glow plugs from NGK are the required energy source. Before the start of the engine, the glow plug is energised and the glow tube heats up to more than 800 °C. This heat improves the engine\'s ability to cold-start considerably. The glow plug\'s heat development also optimises the combustion, so that the development of smoke and other emissions is reduced.DIMENSIONSHex (mm):12Thread diameter (mm):M10Thread pitch (mm):1.25Overall length (mm):79.5Heater tube length (mm):17.5Terminal (mm):M4 threadedMarked voltage :11 VIf you are unsure as to whether this is the correct part for your vehicle, please don\'t hesitate to contact us. Alternatively please use the cross reference table above.