This is the O. S. Max LC4 Medium Long Reach Glow Plug.  Designed for use in .12-.15 and .18 size engines used in monster trucks such as the original and newer 2.5 Traxxas T-Maxx. 

Features:

• Like all O. S. Max glow plugs, the LC4 is tough enough to take the heat and provide hassle-free starts and outstanding durability 
• High-performance long reach glow plug suitable for 1/10 scale off-road applications that require constantly varying speed 
• The LC4's longer reach extends coil farther into the engine's combustion chamber improving combustion for better idling and good acceleration throughout the throttle range 
• Compatible with Traxxas's EZ-Start system 
• Hot heat range for fuels with 5%-20% nitro content 
• No idle bar