Ford Steering Rack Limiter for 1987-2004 Mustangs.
Mustang owners who install wider tires/rims on the front of their Mustang or lower their Mustangs with lowering springs always run the risk of rubbing at full steering lock (U-Turns / Tight Turning Radius). The steering rack limiters will prevent this rubbing by slightly limiting the steering just enough to keep your tires from rubbing.
A stock steering rack already has these limiters in the stock setup. Ford uses them so that they can share the steering rack among many different vehicles, with different body style and wheel sizes. However most aftermarket racks do not include these limiters.