These extend from either side of the user's dominant hand, and are attached to a device that's worn around the wrist. The idea behind them is that (among other things) they could allow users to perform tasks that usually require two hands, using only one. As an example, the extra fingers could grip a jar while the other fingers unscrewed its lid, or they could hold an envelope down while the others slit it open – both of which have already been demonstrated in the lab.