3.5mm; Length: 3.9. Ball end hex keys save time by allowing you to insert the ball end into the screw head quickly, from up to a 25deg angle, even when working in blind locations. You"ll find ball end tools work efficiently, even near obstructions. High-quality machining means smooth rotational action, extended tip life and reduced fastener wear. Ball end tools are made of Protanium high torque steel, which is up to 20% stronger, with more torque and twice the wear resistance of standard grades of steel. Protected with ProGuard corrosion-resistant finish. U.S.A. Total Hex Keys (qty.): 1, Hex Tool Type: Ball end.