This extension spring is sourced directly from the original equipment manufacturer for Black and Decker and DeWALT drill presses. It is an important component that applies tension on the knob for the edge guide. Over time it may wear out and lose tension eventually requiring a replacement. To ensure the correct installation of this hardwa...Read morere, check the diagrams of your specific model. This high-quality spring is made of a durable metal and is sold as an individual item. Replacing it does not require any tools, remove the knob and replace the spring.