Internal micrometer adjustments have positive internal locks. The FP is strong, rugged, dependable. The alloy used to manufacture this sight has a tensile strength of 85,000 pounds. Yet, the FP is light and compact, weighing only 1-1/2 ounces.  For big game hunting, the FP will outsell all other makes and models of receiver sights put together.  FP-RU77 Tits: Ruger 77 Bolt Action