For Serpent Cobra Square Machined Delrin Shock pistons, the Already understood Serpent Cobra big-bore 16mm shocks. The Machined Delrin Shock Pistons 16mm are completely Round and produce Supersmooth Shock action. Holes 1.2mm loaded in Sets of 4. Associated things Shock Pistons Conical 6 Hole (4) (#600349) Shock Pistons Conical 8 Hole (4) (#600350) Shock Pistons Conical 10 Hole (4) (#600351)