The 5S 5000 25C nano techs have served me well for 2 contest seasons, going on a 3rd now. The 2 oldest sets will stay on for practicing and I am adding 2 new sets for this year's contest season (the youngest set from last year stays in the contest mix). There is no puffing or other defects, just normal wear & tear (all year round practicing). These work well if not abused fom my experience at the intermediate level of competition. YMMV, as always, but at this level of price to performance, I'm a satisfied customer. A few masters pilots have flown my planes through their schedule with no shortage of juice so that speaks well for these particular nano techs. That said, I'll stick with the 5000's and see no need for more than 25C (though I get the IR thing). Cheers!