The Wasp uses a glowhead insert, not a standard plug. Replacements are readily available, though they cost about $6. Its retainer/head is threaded the same as C*x/Norvel/VA engines, so you have some alternatives available. The obvious one is C*x glowheads. Also a standard plug adapter head can be purchased from MECOA anytime you want to cut the power output down. Of course, the bright side of this is that the Galbreath/Nelson adapter head fits and gives a performance boost!