John it is the normal insert for Tamiya or Yokomo Sedan 24mm tire. It is the closed cell shaped insert.
50D insert is black.
I never used the swaybars on my M03 it is out for a friend to run at Nats this year and I know he is just starting to use them. I relied on the M04 most of the time and did not spend alot of time developing the M03 but without bars it has been great I would think you could shave a 1/10 or 2 with the bars.

Tom not sure if Fred is going to or not. I thought I saw only 1 class in the last rules release.