FPS CNC ERGAL Double O-Ring Ball Bearing AEP Piston Head (TPAEP). The FPS ERGAL piston head is a great upgrade that will increase the efficiency of airflow through the cylinder. This piston head has ports on the front to push out the o-ring as it moves forwards, this ensures that all of the air in the cylinder is being pushed out to propel the BB. The ball bearings help reduce tension created by the spring compressing and expanding, this combined with a ball bearing spring guide is the optimal set up to keep your spring in good shape. Each FPS piston head is made of ergal (aluminium 7075). The piston head is constructed out of CNC ERGAL for durability and precision. This product is designed and manufactured entirely in Italy, by technicians who have years of experience in the repair and modification of airsoft replicas and guns. Weight: 5.13 grams 100% MARUI COMPATIBLE 100% MADE IN ITALY