The XS Sight System Low Weaver Backup Base, Ghost-Ring Aperture Sight is a fast, alternative, open sight that will save your hunt if your scope fails. Perfect for use on in-line muzzleloaders when hunting no-scope areas. Attaches in just seconds, without gunsmithing (if the receive is drilled and tapped), to any Weaver-style base. Specifications: - Low - Fits: Any Weaver Style Base - Fully Adjustable Windage and Elevation - No gunsmithing needed if the receive is drilled and tapped - Includes: Nylon Test Posts to help determine required front sight height