Designed for the USMC SSOT contract, the FOS (Field Observation Scope) has the durability that U.S. Optics is known for, but in a Field Scope. 15-40X magnification allows the operator to view targets at extreme distances as well as range them at any magnification setting with the FFP reticle. With over 3" or eye relief, the FOS can be used with sun/safety glasses, gas masks and nuclear/biological disaster suits.