Basic Armour is the standard issue armour issued to Xenonauts troops. It is basically a simple uniform with a metal helmet, offering virtually no protection. But this armour does not weigh down the user, allowing them to carry heavier equipment.
Basic Armour weighs a mere 7 kg. It provides no protection.
Basic Armour is the only Armour on offer at the start of the game. Normal Kevlar Armour is ineffective against the alien weapons, thus combat doctrine is based around speed and usage of cover to mitigate alien plasma fire. The player should do everything in their power to place their soldiers in the best available cover possible, and avoiding leaving their soldiers exposed. A single shot from a plasma pistol is sufficient to usually kill a soldier in a single hit, rarely a soldier might survive a plasma blast, albeit with little health.
Despite these disadvantages, basic cloth does offer some unique advantages for the early and mid game. Due to it weighting very little you can afford to have the solider carry heavier and more numerous equipment than they otherwise could if the soldier was wearing heavier Armour, in addition to the fact that Basic Armour is free.
It can be viable, if not necessary, for specialist soldiers, such as rocketeers, machinegunners or snipers, to forgo superior armour and use Basic Armour to be able to carry heavier weapons and equipment.
Nonetheless, frontline soldiers would appreciate being given better Armour when possible.