This is a set of optional 1.5x2 shock pistons. The larger the hole the less "pack" the shocks will have when compressed, which can be used to fine tune the handling of the buggy in the bumps and over the jumps. When a shock piston has smaller holes, it will have more "pack", which means the shocks will feel stiffer under high compression speeds (ie: landing off a jump or hitting a bump at high speed) compared to pistons with larger holes. Using thicker oil will not affect the shock "pack", but make the shocks slower to respond for both low and high speed bumps.
These pistons also fit the Thunder Tiger EB4 S3 shocks and are a good upgrade to consider for very bumpy tracks to replace the two stage pistons in the Thunder Tiger shocks.