Phase I clone trooper armor represented the standard issue armor utilized by the clone troopers within the Grand Army of the Republic during the initial stages of the Clone Wars. Constructed by Kaminoan armor specialists, this armor comprised white plastoid plates layered over a black body glove. As time passed, the Phase I armor was superseded by the Phase II clone trooper armor, an improved design that better accommodated the human form.
The Phase I clone trooper armor, a creation of Kaminoan armorsmiths for the clone troopers of the Galactic Republic, benefited from design input from the bounty hunter Jango Fett. It consisted of twenty precisely fitted plates crafted from a lightweight plastoid-alloy composite. These plates were secured to a black temperature-regulating bodysuit using magnatomic gription panels. Furthermore, the bodysuit was pressurized, offering temporary protection against the vacuum of space, while also shielding the clone from extreme temperatures.
The armor of Phase I incorporated splashes of color to indicate the military ranks of clone trooper officers, a feature deemed useful for non-clones and even clone troopers whose helmets were damaged. However, this convention waned as clones developed greater individuality, influenced by the Jedi. Customized colors and armor eventually signified a clone's personal identity; Clone Commanders like Cody sported personalized armor to distinguish themselves.
The design of the armor shared similarities with Mandalorian armor, notably the helmet featuring a distinctive T-shaped visor. Despite its advantages and Fett's design contributions, the Phase I gear was ultimately a product of the Kaminoans, who lacked a comprehensive understanding of human ergonomics and physiology. Consequently, the armor restricted movement, caused discomfort during extended wear, and proved awkward for sitting.
Phase I armor could be enhanced with additional equipment, including pauldrons and kamas. Inside the Phase I helmet, a clone trooper benefited from a life support system, a tracking device for monitoring troop movements, and a display screen integrated into the helmet's viewplate. The helmet also included a comlink, with a comlink antenna positioned on the helmet's crest. Clones could further customize their helmets with attachments like macrobinoculars, a rangefinder, or a visor.
The armor specialists of Kamino conceived the Phase I armor drawing inspiration from the Mandalorian armor worn by the clone soldiers' template, the bounty hunter Jango Fett. Fett's input shaped the armor, which debuted concurrently with the initial deployment of clone troopers at the First Battle of Geonosis. By the Battle of Mon Cala, it was gradually being replaced by Phase II clone trooper armor, which was more comfortable and capable of supporting more specialized equipment. Some clones, having thoroughly customized their original gear and grown accustomed to it, resisted the transition to the new armor.
During the Battle of Mon Cala, Clone Captain Rex had yet to adopt Phase II armor, but one of the clones serving alongside him aboard a Venator-class Star Destroyer had. During the Imperial Era, a clone trooper still equipped with Phase I armor participated in a battle within a sandy environment alongside a 7th Sky Corps clone paratrooper, a 501st Legion clone trooper, and an All Terrain Tactical Enforcer.
In the DVD audio commentary for Star Wars: The Clone Wars, Dave Filoni mentioned that, even though the clone troopers' helmets contained transmitters and receivers, the act of the characters pressing buttons and holding up wrist-mounted comlinks visually communicated to the audience that the characters were communicating with each other.