The same Glow Devil R/C Long , Thunderbolt R/C Long, Thunderbolt 4 stroke plug, SIG R/C Long that you would on any other larger stunt engine. The LA and FP.25 both take the same long reach plug as larger engines. Mikegoesflying .com has the Thiunderbolts, Sonic Tronics has the Glow Devils, and SIG and some hobby shops sells the SIG products.
HAPPY THANKSGIVING!
Dan McEntee