The SRB chassis is possibly the most iconic chassis by Tamiya. It's built on a FRP plate with front and rear suspension bolted on. Both ends have torsion bar suspension and have oil-filled dampers (Tamiya's first). The radio box and rear mounted gear box is supposed to be water proof, it's more like splash-proof. The radio box is made from clear plastic. The SRB chassis had many variations from the early production (Mk.1) with slimmer front trailing arms,screws instead of pegs as spring retainer, different gearbox moulding, etc, etc. There is no definitive point in time where the desing shifted from Mk.1 to Mk.2. The various changes were introduced during production. Now the re-released Buggy Champ and Sand Scorcher has even more changes, nearly all the parts has been modified compared to the old Mk.1 and 2. The above picture shows a Mk.2 Rough Rider chassis.