The Series 4000 is the model of Mechanoid of which Kryten and Able is. Developed by DivaDroid International was much better received than the Series 3000 mechanoid. The Series 4000 model looks like robots whereas the Series 3000 model looked too much like real humans - which caused a disturbing reaction among consumers. "RD: Out of Time" The next up in the DivaDroid line was the Hudzen 10 which broke the "series" naming tradition and featured far superior skills, though a tendency to go insane during over-long space trips as shown in "The Last Day".