Truglo Opti-Speed Velocity Calibrated BDC 4x32mm Crossbow Scope - OPTI Speed takes your crossbow even further with a 20-100 yard BDC reticle. a speed calibrated range from 215-450 FPS, and an illuminated reticle for enhanced contrast against dark targets. Glass-Etched Reticle Can Be Used With Or Without Illumination; Enhanced Crossbow BDC Reticle Compensates For Bolt Drop And Provides Accurate Hold-Over Points From 20-100 Yds; Speed Calibrated Magnification System Scales The Reticle And Target Image To Match Bolt Velocity (215-450 FPS); Nitrogen Gas-Filled; Fully-Coated Lenses Provide Maximum Brightness, Clarity, And Contrast; Adjustable Rheostat Brightness Control; Durable Leaf-Spring Click Adjustments For Windage And Elevation; Wide Field Of View; 1/2-MOA Windage / Elevation Adjustments; Weaver-Style 30Mm Rings Included; Battery Included (TG988C, 3V-CR2032);