FYI guys you are definitely going to want the aluminum rear arm mounts the stock plastic ones are fat and limit ur motor adjustments also they seem to pull out during racing so make sure you check them after every run . i found one of my older aluminum arm mounts and put it on. so next time the car will be more consistent during the race . and with the aluminum arm mount i can run the pinon i want to . i am able to go from a 22 tooth to a 31 where as with the plastic i was only able to use the 29 tooth as my smallest .