The 80ST and 80STG are 4-pin UX-base full-wave power rectifier vacuum tubes utilizing the classic ST-12 shoulder glass envelope. Introduced by RCA in 1927 under the original type 80 designation, these tubes were widely used in 1930s and 1940s mains-powered console and tabletop radio receivers to convert AC voltage into smooth DC power for filter circuits. The "ST" and "STG" designations explicitly denote the shoulder-type glass bulb design ("G" specifying glass construction), distinguishing them from earlier globular S-17 glass versions. Featuring dual directly heated filaments, they operate on a 5.0V filament supply and fit standard 4-pin UX sockets. The 80ST series serves as the 4-pin predecessor to octal rectifiers like the 5Y3G. Available NOS and tested used.