The band's fourth album, Stained Class, had less of a psychedelic sound and was rockier sounding. This was the first album to have drummer Les Binks, who had a drumming style that was liked by many fans, and is thought of as important for improving the band's sound. The fitth album, Killing Machine (called Hell Bent for Leather in America because of the original title suggesting murder) was also rockier sounding but had shorter songs. "Hell Bent for Leather" from the album is one of the band's more popular songs. Les Binks left after this album.