Developed for the U.S. Special Operations Community, the Geissele Automatics Super Select-Fire (SSF) Trigger is a non-adjustable two-stage combat style trigger. It features a semi-automatic mode offering precise and accurate control from the two-stage SSF trigger. In fully automatic mode, the single-stage SSF trigger offers continuous pull and quick hammer release. Each trigger is precision EDM wire cut from heavy-duty tool steel with curved bow and durable black finish giving you the reliability and durability you can depend on. The SSF is compatible with M4 / M16 pattern rifles with MIL-SPEC .154" trigger pins.