A5, A3, and #8. the A5 is a cold plug, the A3 is a hot plug, and the #8 is their "medium" plug.

if it's really hot where you live (like it is here), you'll want to stick with an A5 (or any cold plug)

and tat-breakin usually beats the crap out of a glow plug, on any RC engine. after your engine is broken in, you should have a lot of trouble-free runs out of your car