Tougher Armor is a technology that is unique to the Rebel Alliance, and can be researched at the War Center in Tech Level 4. It costs 250 Food and 125 Nova, and gives +50 Hit Points to Mounted Troopers and +30 Hit Points to all other Troopers.
This technology makes the Rebel Troopers sturdier, and is a must-have if the player relies on Troopers in combat. It is less effective than the Droid Upgrades of the Confederacy and the Self Regeneration of the Wookiees, but also far cheaper than either of those upgrades.
"By developing new and improved defensive technology, the Rebels can grant all their Troop Centre units additional hit points, making them much tougher in battle."