This is an optional Axial Dig Upgrade Set, and is intended for use with the Axial Wraith 1/10 scale Rock Racer. The Axial Dig Upgrade Set works with the Axial Dig Transmission Case. The Dig function which, when installed, gives you a three function transmission. The optional Dig Upgrade Set comes with servo linkage, slider parts and an output shaft. When installed you have 4x4, 4x2 (freewheel) and Dig (rear locked) capabilities. This aids in extreme climbs and descents and turning a tight radius. (not included - extra servo. Three channel radio system also required).