Extraction tubules were a pair of flexible devices used by the Borg, similar in appearance to assimilation tubules. However, whereas assimilation tubules were used to inject Borg nanoprobes into victims to initiate their assimilation, or interface with technology, extraction tubules were used to extract DNA or other information from a biological lifeform.
In 2375, a transporter accident created a Borg maturation chamber aboard the USS Voyager which utilized a pair of extraction tubules to remove DNA from Ensign Mulcahey which it then used to create the Borg drone known as One. The procedure left residual nanoprobes around Mulcahey's injury implying some kind of exchange of material, whether intended or not. (VOY: "Drone").