In 1989, S&W redesigned the entire line of 9mm semi-automatic handguns. The 3904 is chambered for 9mm Parabellum. Has an 8-shot detachable magazine and 4" barrel with a fixed bushing. Frame is alloy. Triggerguard squared for two-hand hold. Magazine well beveled and grips are one-piece wrap-around made of Delrin. Three-dot sighting system is employed. Discontinued.