R4-S2 was a smaller-than-normal red and gold astromech droid. It belonged to Twi'leki scouts who set out to explore the moon of Uffel, as part of their vessel's droid pool. Its responsibility was as a maintenance droid which made minor repairs and kept the electronics system functioning properly. It had an extendible "neck" by which it could raise its head-cone to see into higher levels of the ship.

When the scouts' ship crashed in 90 BBY, R4-S2 was one of three droids which managed to survive and repair itself, along with fellow astromech R4-J9 and the administrative droid QS-2D. The droid went on to work for QS-2D, surveying mineral deposits of the moon and helping to set up mining operations.

R4-S2 was active in 31 BBY.