The Weaver Classic Top Mount Aluminum Base #401 is a rugged, one-piece scope base designed for factory-drilled Smith & Wesson and Taurus revolvers. Made from high-strength aluminum with a gloss black finish, it is precision-machined to tight tolerances for a secure, custom fit. This base is compatible with Weaver-style rings and provides a solid mounting solution for optics on S&W 29, 629, 625, 686 and Taurus L, K, and N Frame revolvers. The rear sight must be removed for installation, and the revolver must be factory drilled and tapped. Not suitable for X-Frame revolvers.