Williams Receiver-Mounted Notch Blade Sight. Only for models that have been modified with the AS2250-013 receiver kit. Including Pistol models 1740, 2240 1377, 1322 . This sight is strong, rugged and dependable. Despite light-weight 1-1/2 oz. compact alloy comprisal, this sight has a tensile strength of up to 85,000 lbs. Includes target knobs for easy adjustment, as well as internal micrometer adjustments with positive internal locks.