Sig Sauer SIERRA 4, Rifle Scope, 4-16X Magnification, 44mm Objective, 30mm Main Tube, BDX-R2 Digital Ballistic Reticle, 0.25 MOA Adjustments, Black SOSBDX44111 The SIERRA4-BDX riflescope simplifies shooting at distance by connecting to BDX-equipped rangefinders to deliver an illuminated holdover dot specific to your target distance, ballistic performance, and environmental conditions. With a digital focal plane and 194 LED hold points, the SIERRA4-BDX brings unmatched accuracy, connectivity, and clarity to the field.