The Glide Gear SYL-960 is an amazingly versatile track dolly. This unit will allow you to make world class professional films for a fraction of the price of some of the other upper end track dollys on the market. At the heart of the new Glide Gear SYL-960 track dolly system is the advanced sliding swivel wheel system. These wheels are not only full 360deg. swivel, but also able to freely slide within the wheel housing in any direction by an extra 1". This means that the track can be as uneven as 2" in places and still not effect the smooth operation of the Glide Gear SYL-960 track dolly. In addition to all of these features, the Glide Gear SYL-901 is a hybrid that can easily be converted into a rolling camera dolly with the included regular swivel wheel castors. Each swivel track wheel assembly comes with four track wheels (4-wheels) for maximum stability and each castor wheel has 360deg. swivel and locking mechanism. These track wheels are made for movement along a track, they have the most surface area in contact with the track surface possible.