1/4 3/8 UNC Thumb Screw Clamping Lever Wing Knob Hand Grip Bolt Adjustable Metal
1/4-20 UNC, 3/8-16 UNC （Unified National Coarse Thread）. – Thread Size: 1/4-20 UNC or 3/8-16 UNC. Adjustable knob screw is spring loaded which can be pulled out or turned to a more friendly position after being tightened.