4-KT was originally a medical droid, and was one of the first droids that Riboga the Hutt sent QS-2D to set up its mining operations on Uffel. As Uffel had no use for a medical droid, 4-KT was reprogrammed for droid development, and ended up working with G-8Y5. It enjoyed its creative work, and would sometimes continue to work until it had drained its power cells.

4-KT resembled a silver humanoid skeleton with bright yellow eyes. Its head was slightly oblong because it had an extra boxlike appendage attached to the rear. It had ten long fingers on each hand, which were capable of incredible precision. 4-KT typically held the extra fingers outstretched when not in use.