2 x Replacement 6+6 Hole Bypass1 Pistons. 6+6 piston is the same as the standard 6 hole piston but has 6 additional dimples that can be used to add smaller low speed bleed holes for more chassis roll around tight corners. Some racers will drill out all 6 dimples at .5mm (.020”) or just 1 hole at 1mm (.040”).