When the five scientists who designed the XXXG-00W0 Wing Gundam Zero in AC 180 went their separate ways, each of them took copies of the plans for their original Gundam design. The Gundam Sandrock, created by Instructor H using the resources of the Winner family, is the fourth of the Gundams sent to Earth in Operation Meteor. This powerful, heavily-armored mobile suit is perfectly suited to the desert environments of the Winner family's Middle Eastern homeland. Its regal appearance also suits the noble heritage of its pilot, Quatre Raberba Winner.

Of the five Gundams launched in the "new" Operation Meteor, "Gundam 04" (as the Sandrock was code-named by OZ) was the most heavily armored, further lending to its durability despite its almost indestructible gundanium alloy construction. The Sandrock was also the strongest - better built to handle its two very large and heavy "heat shotels," which worked as both an excellent pair of melee weapons and as throwing weapons. The heat shotels can be combined with the Gundam's backpack and shield to form an immense pincer weapon called the "Cross Crusher." Topped off by a pair of head vulcan guns and two large homing missiles in its shoulders, the Gundam Sandrock was nothing but tough through-and-through.

Source: Gundamproject.com, New Mobile Report Gundam Wing