New 4-hole large-bore shock pistons designed specifically for the wider XRAY shock absorbers. The newly-redesigned pistons use a new production process to improve roundness, ensuring perfect piston movement in all four shocks. These pistons have four (4) straight holes (not tapered) in sizes of 1.3mm 1.4mm and 1.5mm in every set.
The 4-hole pistons with the same hole diameter have increased oil flow compared to pistons with fewer holes (for example, 2-hole pistons). This allows to use the thicker (stiffer) shock oil, which will allow for different damping characteristics.
Source : Xray