The Wagtail II was the first attempt to create a standardized ExoShell that could easily be modified by its pilot to fit their unique style of combat. This unit was designed off of the ExoS-003 "Wagtail", and ExoS-005 "ReZEL". The unite showed a huge performance boost over the previous Wagtail model. It was a fairly successful ExoShell in its stock configuration. But because it was such a simple design, it was harder to adapt it to more extensive modifications. Often a tech crew would have to not only create the new hardware for the unit but completely rewrite the central computer systems, which would lead to hardware/software issues.