Aiming to improve on the default design, the Leofoto SF-03 is a replacement for the original foot supplied with the For Sony lenses/SONY FE 400MM F/2.8 GM & 600MM GM F/4.0 GM LENSES. The SF-03 replaces SONY's original lens collar foot and provides a lower profile and a lower center of gravity for a better balance. Two safety stops are located on the bottom of the foot, which prevents accidental lens release when a quick release receiver clamp is partially open