SIGHTRON SIIB 4-16x42MM Dot Reticle Sightron’s SII Big Sky line of rifle scopes have been designed and built to meet the demanding needs of both competitive shooters and hunters who shoot long range. These include a one-piece tube, ExacTrack adjustment system, and Zact-7 Climate Control Coatings. Each scope has target knobs and an adjustable objective lens. Eye relief is between 3.7 and 4 inches. Specifications: Magnification: 4-16X Objective Diameter (mm): 42 F.O.V. FT. .