This Cold Steel 39FK Double Agent I Fixed Blade Knife Satin Plain Edge 39FK. The Double Agent neck knives possess a significant set of advantages worth noting. Designed by Zach Whitson, with either a Karambit or Clip Point blade style, they’re thin, flat, and super light (a little over 3 ounces including sheath). This makes them easy to conceal and very comfortable to wear. Their most audacious and notable feature, however, is their double ring handle design. Slip an index finger through the front ring nearest the blade and your pinky finger through the rear ring and close your fist to obtain a forward grip and vice versa for a reverse grip.