The black S2.RA6E1 End Stops with Power Cable Holder from ARRI come in a pack of 4. These plastic end stops can be attached at both ends of a T6 type rail to prevent carriages from leaving the rail. They also feature cable ties that can be used to secure power cords to the end of the rail.
Note:
Moving rails require end stops in the upper and lower section of the rail. End stops need to be mounted into the holes after all carriages have been installed.