The fastest I've used have been Putnam Duo 2's. For our RCGT class, I put the 17.5 in my car, tossed a 3.8 FDR at it with 0 timing, and never got passed yesterday in racing (came off at 145). The 21.5/open ESC guys had a bit more on the straight but that's it. (club racer, no sponsorship here BTW)