I run the 4x1.8 with Losi 50 in the front and 35 in the rear and have had great luck with them. I use to run the 6x1.5 and 6x1.6 Pistons but like the idea of fewer holes that are larger which should stay soft at lower speeds but pack up nice at higher speeds. Lately I have been running the 3x2.1 with PT 750 in the front and 700 in the rear in my SCT with really good success. I like how the truck rolls and jumps but still packs up. When running the 6x1.5 I was having problems with it being too stiff or too soft.