3D Printed Spring Assisted Skull Pocket Knife Fast action spring assisted knives give you a tactical advantage when every second counts. Quick, one handed opening with inner spring assist. Product Specifications: Textured synthetic handle with 3D design and steel liners. Combo window breaker & belt/cord cutter on end of handle. Combo edge, partially curved blade. Sharpened 440 stainless steel blade with black finish. In-line open lock. Includes pocket / boot clip. 8 1/4 in. overall opened, 3 5/8 in. blade, 5 in. closed. How are Spring Assist different from a Gravity Knife or Automatic Switchblade Knife? Gravity or Switch Blade knives feature a button, level, or other type of switch that releases a spring pressure to automatically open the blade. On a Spring Assist knife, there is no separate button or switch. Instead, you apply pressure to part of the blade to begin the opening process. This is usually a small bump of metal which sticks out under the knife, making it fast and comfortable to use. Once you press on that part of the blade, it automatically opens and locks into place. Since the action of opening the knife is started by pressing the blade metal, instead of a button or switch, it is considered to bypass the laws which ban switch blade knives.