great engine, I orginally purchased 2 engines and installed them on a Twinstar; they were at least 15mph faster than the magnum 25XL I have ben flying the 25XLS engines for the past 4 months and they are still running great, also they have seals in the muffler joint so they don't leak. I like them so much I purchased 2 more; I plan to put all 4 on a 90" B-17