*PS: Please note: installing parts / assemble /fitting airsoft gun will need intermediate knowledge; for expert or airsoft gunsmith. Please refer to your airsoft gunsmith for proper installation / fitting. Fitting may be needed as the condition of each airsoft gun might be different. Regular maintenance is needed for all airsoft guns in order to keep it in good working condition and reduce wear out issue on parts. The actual performance is based on the overall setting on your airsoft gun. Please consult your airsoft gunsmith for advising. Strong Screw glue is needed for installation. Use a drop of screw glue when installing the screw and wait for it to dry out overnight. Damage could be caused to the screw thread if screw glue was not used.