The Gitzo lateral arm attaches to Gitzo tripods and most other brands in order to adapt the tripod for macro (close-up) photography for which the camera needs to be positioned at angles or distances beyond the range of the typical tripod alone.  It is helpful for outdoor photography in remote areas in which bringing heavy gear is impractical.  It can also convert the tripod to a copy stand.  This lateral arm is very gently used with minimal scratches, etc.  The adjustable length from the tripod head is from approximately 2' to 18."  This is a somewhat rare, but very useful item.  NOTE:  The tripod pictured is not included for sale.