Ensuring an absolutely perfect grip on your favorite Vac-U-Lock dildo, plug or probe, the Knuckle Up is completely unique, extra user friendly, and a truly great addition to the Vac-U-Lock family. Taking the shape of classic brass knuckles, the firm ABS plastic grip fits through the fingers and provides a solid handle for ultra precise maneuvers once a compatible toy has been attached to the universal plug up top. Simply slide your penetrator of choice on, and enjoy. Fits most hands.