Pre-marked focus rings work with the Teradek RT's Lens Mapping features on compatible Controllers. Be sure to select the appropriate pre-marked ring for your lens. CTRL.1 introduces built-in lens mapping, which allows for auto-calibrating lenses to pre-marked focus rings and accessing configurations at any time with the touch of a button. Pre-marked rings cover multiple lenses, saving time on set from manually calibrating after every lens swap. This addon is for metric unit measurements and works only with CTRL controllers