Shock pistons with split hole sizes achieve a new damping progression unlike a traditional piston.   For the case of the 3+1 pistons, the added +1 small 1mm hole gives the shock lighter initial damping to prevent wheel hop, and to prevent the shock from binding up after huge landings.    The 3+1 pistons are especially effective when using the Associated Kashima Coat (TM) optional shock bodies.   The Kashima coat bodies tend to have a thicker damping feel because of the thickness and type of coating used.    

Precision CNC machined 12mm 4 Hole Piston, split 3+1 with 1.4mm and 1.0mm hole and Flat profile.   These pistons are sold 2 pcs per package and each pair comes with our Shock Piston Tunning Guide.  The Tuning Guide explains the handling characteristics of each piston going from the lowest damping (low resistance) to highest damping.

These pistons are great in 2wd front OR rear (recommended 32.5 front, 30wt rear oil), and 4wd front (recommended 35-37.5wt oil)

Fits V2 12mm shock shafts by Team Associated with "screw-on" piston (comes in B6 and B64 series kits).