Hi Randy, I've received several OS glow plugs, type F. On the paper work it states they are for four cycle engines. Do you know if anyone has tried these plugs for control line engines? Being for four cycle engines I believe they would be a hot type plug. Most my stunt engines I use the enya #3, which is a hot plug. What do you think would be the worst that could happen running one of these plugs? They look a lot like a long reach type plug, no idle bar, just a long coil. I also received several McCoy four cycle plugs, they look very much like the OS plugs. Just another dumb question, Gary