MAXX's new AEG cylinder heads are CNC machined out of aluminum and then coated and engraved. Their new CNC machined aluminun cylinder heads are machined to proper tolerances to fit in most V2 and V3 gearboxes, whereas other brands like SHS and Ace1Arms may sometimes require modification for optimal fit within the alignment notches. They also use two O-rings against the cylinder for an excellent air seal.