A3 is pretty much the standard "regular" glow plug... i use them alot, and they are pretty good..
it seems like the Hanger 9 plugs last a bit longer,,, but cost more,,
and ENYA 3's are a club favorite,, but again, cost more,,

like alot of things in this hobby, you get what you pay for..

tower hobbies plugs work, but wear out pretty quick...