The XS Lever Rail upgrades the Henry .357 to allow for mounting of an optic in multiple positions. Fits Henry Steel Frame, Big Boy, round barrel carbines chambered in .357 Mag. (Does not fit Big Boy .357 Mag X Carbines.) Lightweight, anodized aluminum rail is machined to Picatinny specs and allows scope mounting directly over the receiver, or forward for scout scopes or red dot sights. Installation requires removal of factory rear sight. All screws torque to 20 INCH-pounds; over-torquing can fracture or break screws. The XS Sights Lever Rail will not work on Henry rifles with brass receivers or octagonal barrels. The rail can not be modified to work on them. The XS Sights Lever Mfg: Xs Sight Systems