UAC Aluminum Hop-up Chamer For TM M&P9 - Constructed with 7075 aircraft grade aluminum provide excellent durability. Manufacture by precision CNC to ensure the chamber is in tight tolerance for perfect concealment for hop-up rubber and inner barrel. Superb air seal to minimize the energy lost, increase stability and accuracy for each shot. *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.