Used for both military and exploratory purposes, probe droids are specially designed to investigate and report on newly discovered or dangerous areas. Exterior plating materials vary depending on the droid’s task, from hardened or reflective materials for dangerous environments to stealth composites that hide the droid from enemy sensors. Most probe droids are constructed to be as small as possible, and with so much of their design given over to sensors and communications equipment, they often lack the sophisticated intelligence of other droid models.

~ Source: Star Wars: The Old Republic Encyclopedia