This kit contains several gear types designed to help you build advanced mechanical systems. The rack gear will mount on any VEX metal component, mesh with any VEX gear to create linear motion systems. The worm gears allow users to create very high reduction gearing in a small package; these gears will also resist "back driving" which may be useful in some applications. The kit comes with several bevel gears which allow designers to transfer motion "around corners"; you can change the axis of motion by 90 degrees. These bevel gears can also be used with the differential frame to build a differential. This can be utilized to create more efficient "car style" drivetrains.