Williams "Fool Proof" (FP) sight has internal micrometer adjustments with positive internal locks. The FP Receiver Sight is strong, rugged, and dependable while providing a large range of windage and elevation adjustments. The alloy used to manufacture this sight has a tensile strength of 85,000 pounds. Yet, the FP Receiver Sight is light and compact, weighing only 1-1/2 ounces.