1Flexible Design: This flexible shaft extension bit is compatible with regular hand drills and power drills, offering exceptional performance. It can easily bend, twist, and rotate to touch narrow and confined spaces. 21 or 4 Inch: The hex handle drill bit features a 6.35mm (1 or 4 inch) connector, while the internal hex head connector comes in a 6.35mm (1 or 4 inch) size. 3Plastic and Steel Construction: Crafted with premium plastic and steel alloy hex heads, this flexible drill bit extension ensures high accuracy and reliable, efficient usage. 4Easy to Use: With universal adaptability, the drill flexible extension allows you to effortlessly access challenging areas and complete tasks quickly and easily. Its compact size makes it convenient to store in a toolbox or pocket. 5Wide Range of Applications: Specifically designed for narrow spaces, the flexible shaft extension bit is perfect for tasks involving computer cases, electrical cabinets, furniture, appliances, and more.