The Matthews Secondary Offset Arm is for use with their Round-D-Round Doorway Dolly Seat. This device was designed to give the camera operator some extra flexibility and manoeuvrability. It attaches to the shaft that supports the seat and extends away from it, placing the seat off centre. This offers a more comfortable seating arrangement, and opens up new possibilities for creative camera angles. This arm is sold as an accessory, for when you want to use two seats on your dolly.