It was made by high quality spring steel. 2 pieces of spring are able to fit in TM M&P9 and M&P9L respectively which provide stable nozzle movement.
*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.