From Manufacturer
Transport your camera safely and smoothly to perform motion and tracking shots using this Spin Lightweight Platform Doorway Dolly from Proaim, which features four pneumatic wheels, a base plate, two track wheel assemblies, two wheel axles, and two push/pull and steering bars with foam handles. The 11 x 4" rubber wheels absorb shocks, resulting in smoother rides on a variety of surfaces.
Two steering modes enable you to switch between using four to two wheels by using the wheel axles and unlocking the steering lock. The push/pull and steering bars can be mounted separately or together at both ends. One push/pull bar can tilt down 270° and be locked into place for steering. The wooden base plate features multiple threaded mounting points, for adding a variety of separately purchased accessories for expansion options.
The two included track wheel assemblies can slide onto the base as an alternative to the rubber wheels so you can run the dolly on a straight or curved track. The assembled dolly can support up to 661 lb of camera and accessories.