The A11.1 was the standard heavy combat armor used by the various divisions of the Sith Empire army

Imperial Army (Sith Empire) Organization Reconstituted Sith Empire

during and after the Great Galactic War

Great Galactic War Event Great Galactic War (3681BBY - 3653BBY)

.
Typically painted black and dark gray with some elements painted red, the basic kit consisted of a gray jumpsuit and armor pieces that covered the chest, shoulders, back, knees and upper legs. The advanced kit included included a backpack and several extra armor elements - arm and elbow armor pads, heavy knee and shin guards, shoulder shields and extra heavy armor plates covering the wearer's chest and back. It was not uncommon to see a trooper wearing basic kit, but with a few pieces of advanced kit. To protect the head, soldiers were issued either a standard

GE01 A11.1 Helmet Armor Helmet

or heavy

GE01 A11.1 Heavy Helmet Armor Helmet

GE01 helmet.
Standard kit

Matte gray variant with helmet

Advanced kit pieces