Most people swap in an aftermarket differential for added strength and traction. Shown here are three locking differentials available for the Model 20. The Detroit Locker (upper left) is a mechanical locking differential that replaces the original carrier. The ARB Air Locker (upper right) also replaces the original carrier, but it acts like an open differential until it's actuated by compressed air, at which point it becomes completely locked. The Detroit E-Z Locker (bottom) replaces only the spider gears in the stock open carrier and essentially makes the stock carrier act like a locker without adding any strength, but it's a much cheaper alternative to the other two.