The 2018 Microtech HALO VI (High Altitude, Low Open) is the newest version of the first automatic single action, out-the-front (OTF), knife ever produced by Microtech Knives.. The HALO 6, comes with a new safety switch integrated into the firing button so there are no accidental deployments. when deployed, provides the absolute tightest lock up possible. The one handed, fast action open, has fired its way into the hands of thousands of protective agents. HALO’s smooth lines, light weight, and deadly edge, provide a little more than just backup.