The GoCoupler 90deg. allows you to attach an additional GoRail at the end of the SystemGo center column. This allows the GoRail to become height adjustable and you can mount a ballhead and/or other SystemGo accessories to the top of the GoRail. This is ideal for multi camera shoots or for turning your SystemGo tripod into a mobile workstation. The GSC190 is compatible with any 1 series SystemGo tripod. | Benro | | GSC190 90-Degree GoCoupler 1 for 1 Series SystemGo Tripod | Best Buy