OSEP3 OS P3 Turbo Glow Plug V-SP Ultra Hot Off Road.  This is the #P3 Glow Plug for use in the OS Max .21 VZ-R and .12 TR engines. FEATURES: Ultra Hot Type Plug, designed for reliable low speed and more torque at acceleration, suitable for 20% nitro fuel Ideal for novice drivers, allows easy starts and better idling INCLUDES: One P3 glow plug REQUIRES: For use with the .21 VZ-R and .12 TR engines. For installation and removal, use an 8mm nut driver SPECS: Overall Length: 17mm (.67") Thread size: M8x.75mm COMMENTS: This glow plug is different from the conventional glow plug. It is made to fit the Inner Head of the OS .21 VZ-R and .12 TR engines. It has a slight taper on the bottom allowing it to sit flush with the combustion chamber.