[RogerM]

3A pistons are 3 x 1.2mm , 3B are 3 x 1.1 for info.

I run 3 x 1.3 on the rear of the FS when the track has lots of small sharp bumps but no big jumps .... I think you need to go all 3 types but if just buying 2 types then go 3 x 1.1 and 3 x 1.2