The Spartan Locker by USA Standard Gear provides reliable traction at a low cost. The Spartan Locker's patent pending design replaces the spider gears in a standard carrier case, does not use the thrust washers, and has a revolutionary spring - and - pin design that makes installation even easier This style of locker is known as a lunchbox locker because of its compactness. The Spartan Locker features heat - treated 9310 steel internals for enhanced durability. The advantages of utilizing a Spartan Locker are its 100 lock up and affordability, both in initial cost and installation cost. The install is easier on the wallet because the differential does not need to be removed for installation. In fact, some enthusiasts install the unit themselves versus taking it to a shop.