the 16mm ones on the jammin are still better, the 17mm ones just arent as good, they are lower grade ones. but the jammin is better for racing in every way. the jammin is more durable and handles a lot better than the 8.5. i liked my X1 more than my X2! the jammin is extremely easy to setup and one setup worked on every track i raced at, the X2 i had to make small changes at almost every track. all i ran was Ofna products from day one but now im making the switch to O'donnell. i had the X1 and X2 buggy and truggy and a hyper 7 and drove an hyper 8 for a couple of laps and i highly recommend not getting it. the guy that had it ran it one day at the track and sold it.