Current configuration, double bungee visors, HA-LP/PPB oxygen mask.
Except for the supplemental boom mike bracket, the initial configuration of the HGU-55 during its introduction in the mid-end of the 1980's represented standard issue.
There was not a real evaluation, the HGU-55 deemed the best option regarding system compatibility with the just introduced Northrop F-5E Tiger II.
During the evaluation for a "Lightweight" helmet to be provided to jet pilots held in the late 1980s, the HGU-55 was considered as a benchmark against the tested helmets, the prototype S-00x, TITLIS TFC, ZEUS C, and the H-ATS. None of the above helmets had any substantial advantages over the HGU-55, which remained and is still in service today.
The installation of double visors and related oversize visor stops took place at a later stage.