This M120 Tune-Up Kit is manufactured by Hurricane. The approximate FPS you will acheive with this tune up kit is 400FPS (individual's FPS will vary).
These kits are available for AK47 AK Beta AUG M4 MP5 G36 MC51 G3 P90 M16 and Sig airsoft AEGs. This kit comes with a standard bore cylinder. Both the polymide piston head and spring guide have ball bearings. The ball bearings allow the spring to easily rotate decreasing the strain on it. The ball bearings in the spring guide also increase your FPS. Metal 6mm bushings are also included. The air seal nozzle has an O-ring.