BSA 42mm 5-MOA Red Dot Sight: * 11-position rheostat * 5/8" Weaver-style attachment * Magnification: 1X * Object lens diameter: 42mm * Field of view at 100 yds: 77 * Parallax setting: 50 yds * Click adjustment value: 1/2 * Adjustment range: 45-45 * Weight: 0.62 oz * Dimensions: 5.9"L x 4.7"W x 3.9"H * Model# RD42CP