Armstar Corp USA Made Picatinny Rail Scope Mount For 9mm Hk H&k MP SP Rifles. Manufactured by Brugger & Thomet AG. The BT-21241 is an extended, low-profile, and specialized mounting rail designed by Brügger & Thomet (B&T) for the Heckler & Koch MP and SP platforms. While the initial query mentioned “armstar corp, ” the identifier “21241” corresponds to the well-regarded Swiss-made B&T product. Key Features and Specifications. Compatibility: Designed for Aimpoint Micro series (T-1, T-2, H-1, H-2) and similar footprints. Profile: Extended, low-profile design that allows for co-witnessing with the factory iron sights. Length: Extended version, providing more rail space than the standard BT-10266 mount. Material: Hardcoat anodized aluminum, Swiss-made. Weight: Approximately 98 grams. Attachment: Uses a claw mount system that grips the receiver. The B&T 21241 has been reported as hard to find. It is considered one of the best options for achieving a true co-witness with Aimpoint optics on the MP platform.