Produce by Airsoft Masterpiece, this rear sight is design for Marui Hi-CAPA 5.1. All parts are CNC out of high grade aluminum provide the best durability. Material : Aluminum Item Code : RSA-IF *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.