These ships had the ability to cloak using technology Zann bought from the black market. However, due to a side effect of this addition, the ships possessed no shields. To make up for it, they were equipped with extremely thick armor for protection. Because of this extra protection, it dramatically affected its speed, making it very slow.
Also, these ships were equipped with mass drivers, so their weapons would entirely bypass an enemy's ray shields and could overheat their cores to self-destruct if the situation called for it.