This is the P5 Turbo Off-Road Very Hot Glow Plug from O.S. Engines.
FEATURES: Very hot plug for turbo cylinder head engines such as the O.S .21
VZ-B V-Spec and most .18 -.28 cu in (2.9 - 4.6 cc) off-road turbo
head racing engines
Allows leaner needle settings and high-nitro/high RPM running, also
ideal when outside temperature is high