These bases will not fit Henry .30/30 or Henry .45-70 rifles as they are not Big Boy Series(pistol caliber: .44mag.45Colt.357mag.41mag.327Fed Mag) guns. For .30/30 or .45-70 you can purchase a Weaver 63 base online2nd Generation Big Boys are drilled and tapped on the top of the receiver. To determine which generation of Big Boy you have refer to the manufacturer serial number table so you select the correct mount. Instructions on installation of the scope mounts is provided in the packaging. All Henry Scope Mounts accept Weaver style detachable 1" top mount rings.