This is the RP8 Cold Glow Plug from OS Engines for use on Most Turbo 

Head Racing Engines. 

FEATURES: 

For use with fuel containing 25% or greater nitromethane content Cold heat 

rating when outside temperature is high 

INCLUDES: One O.S.RP8 glow plug 

REQUIRES: Glow plug wrench, HCAP2550 

SPECS:  

Overall Length: 17mm (.67") Thread size: M8x.75mm