Uhing drive units have zero backlash whereas backlash is inherent in ball screw systems. Backlash is caused by clearance or “play” between contacting surfaces in ball screws, gears, belt drives and other linear motion devices. To overcome backlash, ball screw users typically preload the nut to keep the balls under steady pressure. Other methods for fighting backlash include active cam mechanisms, shims and other devices which load the geartrain. These methods can be expensive and their performance level deteriorates over time due to wear and tear. In a rolling ring drive, there is continuous point-contact between the bearing surface and the shaft. There is no “play” and zero backlash – even during reversal. Additionally, rolling ring drives have built-in overload protection. If the system is overloaded, the nut will slip, not jam.