The Sigma TS-111 Tripod Socket is a single-locking knob collar that offers more balanced support to the Sigma 105mm f/1.4 DG HSM Art lens when used atop a tripod or monopod. Once the collar is on, it enables the lens and camera to turn on axis in a vertical or horizontal position. In addition, the dovetail foot on the tripod socket is compatible with most Arca-type clamps.