●👷Extends any Forstner shank bit an additional 5-3/8 inches, Helps you use standard forstner drill bits drilling for flat bottom holes or start deep hole turning projects like on larger vases or containers; ●👷The collet inside diameter is 2/5 inch(10.5mm). This tolerance is very tight and designed to accept forstner bits with shank sizes of 2/5inch, 3/8 inch or slightly smaller; ●👷High-carbon steel construction, precision ground and polished, ensuring its sturdy and durable; ●👷Two set screws and hex key included. To fasten the shank in place, use the hex key to tighten these screws; ●👷Triangular Shank Dia.: 3/8-inch, Total length: 6-11/16 inch, Extend Length: 5-3/8 inch.