I have a TT .15, TT.25 pro, TT .25 gp, and 2 of the ST .40. The Super Tigre .40's have many,many flights and have proven to be excellant engines. The Thunder Tiger .25 pro gave me fits with a leaky carb although it has excellant power. Thunder Tiger evidently redesigned the carb to correct this. The other two Thunder Tigers have been very good engines for sleeve type engines. I have a dozen other engines, OS, Magnum, K&B, Royal, Tower. For power, reliability, easy to use, price, my experience says Super Tiger is hard to beat in a 2 stroke.