The K&B is a .29. The Rossi's and Cox Conquests were faster than the Supertiger X .15 back in the 1970's. They have come a long way since then. We were going 160 mph then, now they are over 200mph in FAI Speed (F2A) They use FI for all of it now. I would have to say they are overengineered now, for anyone that is not serious. They sure sound wild though. I saw a Rossi ducted fan motor in the rc canada website for $300. it is a .65 cu in. It is a rear rotor rear ex. probably.